Young gymnasts practice pull-up on a bar at a gymnasium of a sports school in Jiaxing, Zhejiang province April 11, 2015. (Photo by William Hong/Reuters)

An animal rights activist, wrapped in packaging labelled “carne humana” (human meat), participates in a protest against meat consumption to promote vegetarianism in central Barcelona, in Spain, May 22, 2016. (Photo by Albert Gea/Reuters)

In this photo taken Wednesday, December 5, 2018, a woman who scavenges recyclable materials from garbage for a living is seen through a cloud of smoke from burning trash, surrounded by Marabou storks who feed on the garbage, at the dump in the Dandora slum of Nairobi, Kenya. As the world meets again to tackle the growing threat of climate change, how the continent tackles the growing solid waste produced by its more than 1.2 billion residents, many of them eager consumers in growing economies, is a major question in the fight against climate change. (Photo by Ben Curtis/AP Photo)

This combination of April 15, 2013 and April 2, 2014 photos show a police officer clearing Boylston Street following a bomb blast near the finish line of the 2013 Boston Marathon, and pedestrians crossing at the same corner nearly a year later in Boston. (Photo by Charles Krupa/AP Photo)

View of a Spitfire from the cockpit of an He111,somewhere over Southern England 1941 – 2014. (Photo by Adam Surrey)

Malena, 7, looks at Belgian clown Lili Bellule at the pediatric department of the Hopital Erasme at the Universite Libre de Bruxelles (ULB), in Brussels January 27, 2015. The hospital offers performances by musicians and clowns as a form of therapy to help children cope with dealing with the stress and fear caused by hospitalization. (Photo by Yves Herman/Reuters)

A member of a rival team walks during an annual carnival battle with oranges in the northern Italian town of Ivrea February 15, 2015. Dressed up as Middle Age kings' guards, a group of men ride in a horse-drawn carriage and pelt “foot soldiers” with oranges as thousands of people gather to re-enact a Middle Age battle when the townsfolk of Ivrea overthrew an evil king. In a strange twist, instead of swords and cross bows, these days the weapons of choice are oranges. (Photo by Max Rossi/Reuters)

A visitor poses with artist Joyce Pensato's artwork “Mickey for Micky” at the Frieze Art Fair in London, October 14, 2014. (Photo by Luke MacGregor/Reuters)