The world-famous sprinter Usain Bolt, 30, took a break from the track to celebrate Carnival as revellers doused each other with paint in Trinidad and Tobago on February 26, 2017. (Photo by David Wears/Splash News and Pictures)

Tour guides wearing traditional Chinese dress practice smiling by biting chopsticks at Qingming Grand-River Park in Kaifeng, central China's Henan Province on March 2, 2017, aiming to provide better service for visitors. (Photo by IPA Asia via ZUMA Wire)

An AH-64D Apache attack helicopter flies in front of a wall of fire during the South Carolina National Guard Air and Ground Expo at McEntire Joint National Guard Base, South Carolina, U.S. on May 6, 2017. (Photo by Jorge Intriago/Reuters/Courtesy Air National Guard)

A firefighter rests next to fire combat truck during a wildfire at Penela, Coimbra, central Portugal, on June 18, 2017. A wildfire in central Portugal killed at least 25 people and injured 16 others, most of them burning to death in their cars, the government said on June 18, 2017. Several hundred firefighters and 160 vehicles were dispatched late on June 17 to tackle the blaze, which broke out in the afternoon in the municipality of Pedrogao Grande before spreading fast across several fronts. (Photo by Patricia De Melo Moreira/AFP Photo)

A reveler, dressed as a Brazilian national army soldier holding a mock weapon with flowers jutting out of it, participates in the annual Gay Pride Parade in Sao Paulo, Brazil, Sunday, June 18, 2017. (Photo by Nelson Antoine/AP Photo)

A person poses on the track during a fashion competition at the Durban July horse racing event in Durban, South Africa July 1, 2017. (Photo by Rogan Ward/Reuters)

Girls rest on stairs at the China Digital Entertainment Expo and Conference (ChinaJoy) in Shanghai, China July 27, 2017. (Photo by Aly Song/Reuters)

Rwandan refugees cross the Rusumo border to Tanzania from Rwanda carrying their belongings, goats, mattresses and cows, May 30, 1994. The bloodshed that claimed 800,000 Tutsi and moderate Hutu lives began 25 years ago on April 7, 1994, when a plane carrying Rwandan President Juvenal Habyarimana, Burundi President Cyprien Ntaryamira and a French air crew was shot down. (Photo by Jeremiah Kamau/Reuters)