Inside The Beijing International Automotive Exhibition...A paramilitary police officer (right) turns around as hostesses line up for roll call ahead of the Beijing International Automotive Exhibition in Beijing, China, on Monday, April 25, 2016. Tesla Motors Inc. and BYD Co. are among manufacturers showing 147 new-energy vehicles at this year's show.

Qilai Shen/Bloomberg

A paramilitary police officer (right) turns around as hostesses line up for roll call ahead of the Beijing International Automotive Exhibition in Beijing. 

A pot over a bonfire was placed on the tracks of a railway station turned into a makeshift camp, crowded by migrants and refugees at the northern Greek border point of Idomeni, Greece, Monday, April 25, 2016. Many thousands of migrants remain at the Greek border with Macedonia, hoping that the border crossing will reopen, allowing them to move north into central Europe. (AP Photo/Gregorio Borgia)

Gregorio Borgia/AP Photo

A pot over a bonfire was placed on the tracks of a railway station turned into a makeshift camp, crowded by migrants and refugees at the northern Greek border point of Idomeni, Greece today. Many thousands of migrants remain at the Greek border with Macedonia, hoping that the border crossing will reopen, allowing them to move north into central Europe.

Yoga Performance At Tea Garden In Enshi...ENSHI, CHINA - APRIL 24:  (CHINA OUT) Yoga enthusiasts perform at a tea garden on April 24, 2016 in Enshi Tujia and Miao Autonomous Prefecture, Hubei Province of China.  (Photo by VCG/VCG via Getty Images)

VCG/VCG/Getty

Yoga enthusiasts perform at a tea garden in Enshi Tujia and Miao Autonomous Prefecture, Hubei Province of China

Members of the Gruppo Storico Romano (Roman Historical Group) dressed as gladiator stands at Circus Maximus as they mark the 2769th anniversary of the founding of Rome...A member of the Gruppo Storico Romano (Roman Historical Group) dressed as a gladiator stands at Circus Maximus as they mark the 2769th anniversary of the founding of Rome, Italy, April 24, 2016.   REUTERS/Alessandro Bianchi      TPX IMAGES OF THE DAY

Alessandro Bianchi/Reuters

A member of the Gruppo Storico Romano (Roman Historical Group) dressed as a gladiator stands at Circus Maximus as they mark the 2769th anniversary of the founding of Rome, Italy

Chionji Temple Recreates The Moment Of Buddhist Patriarch Death...KYOTO, JAPAN - APRIL 25:  People dressed as 25 Buddhist saints march at the Chionji temple on April 23, 2016 in Kyoto, Japan. This tri-annual ceremony which is split into three parts, a procession, a passing along of the largest prayer beads in Japan and a ritual to the cemetery to pay respects to the dead, is to commemorate the death of Honen, a patriarch of Pure Land Buddhism, recreating the moment when Honen was escorted by Amida-nyorai, the principal Buddha and 25 saints to the Pure Land at the time of his death.  (Photo by Carl Court/Getty Images)

Carl Court/Getty

People dressed as 25 Buddhist saints march at the Chionji temple in Kyoto, Japan. This tri-annual ceremony which is split into three parts, a procession, a passing along of the largest prayer beads in Japan and a ritual to the cemetery to pay respects to the dead 

US President Barack Obama visits Germany...epa05276425 German†Chancellor Angela Merkel (R) tests a Virtual Reality (VR) goggle next to US†President Barack Obama (L) as they visit the booth of ifm electronic (automation engineering) at the Hannover Messe industrial technology trade fair in Hanover,†Germany, 25 April 2016. The USA is this year's partner country at the trade fair. The US President is on a two-day visit to Germany.  EPA/CHRITSTIAN†CHARISIUS

Chritstian Charisius/EPA

German Chancellor Angela Merkel tests a Virtual Reality (VR) goggle next to US President Barack Obama as they visit the booth of ifm electronic (automation engineering) at the Hannover Messe industrial technology trade fair in Hanover, Germany

British astronaut Tim Peake in action running the London marathon while strapped to a treadmill at the International Space Station on Sunday April 24, 2016. While the official 2016 London Marathon was being run in London, Peake ran 26.2 miles on a treadmill in three hours 35 minutes 21 seconds, while aboard the apace station in orbit 250km above the Earth.(EUROPEAN SPACE AGENCY (ESA) via AP) TV OUT

ESA/AP

British astronaut Tim Peake in action running the London marathon while strapped to a treadmill at the International Space Station. While the official 2016 London Marathon was being run in London, Peake ran 26.2 miles on a treadmill in three hours 35 minutes 21 seconds, while aboard the apace station in orbit 250km above the Earth 

Photographers in the press pen as Prime Minster David Cameron welcomes US President Barack Obama to Downing Street

Lauren Hurley/PA

Photographers in the press pen as Prime Minster David Cameron welcomes US President Barack Obama to Downing Street

Ameer Alhalbi/AFP/Getty

A Syrian man evacuates an area following a reported air strike in the rebel-held neighbourhood of Hayy Aqyul in Syria‘s second city Aleppo 

Indians gather around a water tanker...epa05271987 People collect water from a water tanker, in Bhiwandi, some 60 kilometer on the outskirts of Mumbai, India, 22 April 2016. According to reports, 21 districts in Maharashtra are drought-affected. The drought, which has been ongoing for the past five months, prompted 11 states to declare a drought in 2015 and has now choked the growth of kharif (monsoon) crops, including sesame, millet and rice, for the second monsoon season in a row.  EPA/DIVYAKANT SOLANKI

Divyakant Solanki/EPA

People collect water from a water tanker, in Bhiwandi, some 60 kilometer on the outskirts of Mumbai. According to reports, 21 districts in Maharashtra are drought-affected. The drought, which has been ongoing for the past five months 

President Obama Meets With David Cameron At Downing Street...LONDON, ENGLAND - APRIL 22:  President Barack Obama arrives at Downing Street to meet with British Prime Minister David Cameron on April 22, 2016 in London, England.  The President and his wife are currently on a brief visit to the UK where they will have lunch with HM Queen Elizabeth II at Windsor Castle and dinner with Prince William and his wife Catherine, Duchess of Cambridge at Kensington Palace. Mr Obama will visit 10 Downing Street on Friday afternoon where he is to hold a joint press conference with British Prime Minister David Cameron and is expected to make his case for the UK to remain inside the European Union.  (Photo by Dan Kitwood/Getty Images)

Dan Kitwood/Getty

President Barack Obama arrives at Downing Street to meet with British Prime Minister David Cameron in London, England

Britain's Prince Philip, Duke of Edinbur...Britain's Prince Philip, Duke of Edinburgh (L) drives US President Barack Obama (2L), US First Lady Michelle Obama (2R) and Britain's Queen Elizabeth II (R) from the helicopter into Windsor Castle after the Obama's arrived for a private lunch in Windsor, southern England, on April, 22, 2016.  / AFP PHOTO / POOL / GEOFF PUGHGEOFF PUGH/AFP/Getty Images

Geoff Pugh/AFP/Getty

Britain’s Prince Philip, Duke of Edinburgh drives US President Barack Obama, US First Lady Michelle Obama and Britain’s Queen Elizabeth II from the helicopter into Windsor Castle after the Obama’s arrived for a private lunch in Windsor, southern England 

Ultra-Orthodox Jews burn leaven in the Mea Shearim neighbourhood of Jerusalem, ahead of the Jewish holiday of Passover...Ultra-Orthodox Jews burn leaven in the Mea Shearim neighbourhood of Jerusalem, ahead of the Jewish holiday of Passover, April 22, 2016. REUTERS/Ammar Awad

Ammar Awad/Reuters

Ultra-Orthodox Jews burn leaven in the Mea Shearim neighbourhood of Jerusalem, ahead of the Jewish holiday of Passover 

German Chancellor Angela Merkel attends the 500th anniversary ceremony of the German Beer Purity Law (Reinheitsgebot) in Ingolstadt, Germany, April 22, 2016.  REUTERS/Michaela Rehle

Michaela Rehle/Reuters

German Chancellor Angela Merkel attends the 500th anniversary ceremony of the German Beer Purity Law (Reinheitsgebot) in Ingolstadt, Germany

Pablo Porciuncula/AFP/Getty

A particial view of the Nyaragongo volcano taken from Goma, Democratic Republic of Congo 

Jorge Silva/Reuters

A Buddhist monk sleeps in a chair while monks and novices gather to receive alms at Wat Phra Dhammakaya temple outside Bangkok

Carlos Barria/Reuters

Republican U.S. presidential candidate Donald Trump’s hand is seen as he reacts during a campaign event in Harrisburg, Pennsylvania

A bird flies near a torn Syrian national flag in the city of Qamishli, Syria April 21,

Rodi Said/Reuters

A bird flies near a torn Syrian national flag in the city of Qamishli, Syria

Students perform Wu Qin Xi, a type of qigong, during a competition in Bozhou...Students perform Wu Qin Xi, a type of qigong, during a competition in Bozhou, Anhui Province, China, April 20, 2016. REUTERS/Stringer ATTENTION EDITORS - THIS PICTURE WAS PROVIDED BY A THIRD PARTY. THIS PICTURE IS DISTRIBUTED EXACTLY AS RECEIVED BY REUTERS, AS A SERVICE TO CLIENTS. CHINA OUT. NO COMMERCIAL OR EDITORIAL SALES IN CHINA.

Reuters

Students perform Wu Qin Xi, a type of qigong, during a competition in Bozhou, China

Embargoed until April 21, 2016 - 15:00 G...Embargoed until April 21, 2016 - 15:00 GMT / A handout photo released by the European Space Agency shows the Bubble Nebula, also known as NGC 7653, which is an emission nebula located 11 000 light-years away.  This stunning new image was observed by the NASA/ESA Hubble Space Telescope to celebrate its 26th year in space. / AFP PHOTO / ESA/Hubble / STR / RESTRICTED TO EDITORIAL USE - MANDATORY CREDIT "AFP PHOTO / ESA/NASA/Hubble Heritage Team" - NO MARKETING NO ADVERTISING CAMPAIGNS - DISTRIBUTED AS A SERVICE TO CLIENTS / EMBARGOED UNTIL April 21, 2016, 17:00 CESTSTR/AFP/Getty Images

ESA/NASA/Hubble Heritage Team/AFP

This photo released by the European Space Agency shows the Bubble Nebula, also known as NGC 7653, which is an emission nebula located 11 000 light-years away. This stunning new image was observed by the NASA/ESA Hubble Space Telescope to celebrate its 26th year in space