Paramilitary policemen carry tyres as they take part in a training session in Zhangye, Gansu Province, China, March 1, 2016. (Photo by Reuters/Stringer)

People watch as workers inflate a near-10 metre high giant spider by Singaporean artist Jackson Tan in Singapore's Marina Bay financial district on February 6, 2017. The spider is one of several inflatable creatures that will form the Art-Zoo, a section created by Singaporean artist Jackson Tan for the iLight Marina Bay annual light-art festival in the city-state. (Photo by Roslan Rahman/AFP Photo)

In this timed-exposure night photo taken early on February 12, 2017, Mount Sinabung volcano spews reddish smoke and ash, as seen from the Karo district in North Sumatra province. Activity levels have increased in the past week, with Sinabung shooting hot ash clouds into the sky dozens of times, according to the local volcano monitoring agency. (Photo by AFP Photo/Stringer)

A little girl holding her newborn sister waits for their turn in a queue during a vaccination campaign under the supervision of the Syrian Arab Red Crescent (SARC) humanitarian nonprofit organization, in the besieged Syrian town of Douma, Syria, 23 May 2017. According to a statement from SARC, in the city of Douma some 12,809 children under the age of five were immunized in a vaccination campaign to prevent measles and poliomyelitis. The campaign was the first of its kind with the participation of 100 volunteers. SARC has been delivering vaccines to 17 health centers approved for vaccination campaigns in towns and villages in the Eastern Ghouta area. (Photo by Mohammed Badra/EPA)

A woman holds an elderly woman on her back to cross a flooded street after a heavy rain in Shenyang, Liaoning province on July 14, 2017. (Photo by Fred Dufour/AFP Photo)

in Qayyarah, about 31 miles (50 km) south of Mosul, Iraq, Sunday, October 23, 2016.in Qayyarah, some 50 kilometers south of Mosul, Iraq, Sunday, Oct. 23, 2016. Islamic State fighters torched a sulfur plant south of Mosul, sending a cloud of toxic fumes into the air that mingled with oil wells the militants had lit on fire to create a smoke screen. (Photo by Marko Drobnjakovic/AP Photo)

Traders try to control a camel at Pushkar Fair where animals, mainly camels, are brought to be sold and traded in the desert Indian state of Rajasthan November 6, 2016. (Photo by Himanshu Sharma/Reuters)

The damaged battleship USS California, listing to port after being hit by Japanese aerial torpedoes and bombs, is seen off Ford Island during the attack on Pearl Harbor, Hawaii, U.S. December 7, 1941. The 75th anniversary of the attack, which brought the United States into World War Two, is marked on December 7, 2016. (Photo by Reuters/U.S. Navy/National Archives)