An injured national guard officer is carried away by comrades outside the parliament building in Kiev, Ukraine, August 31, 2015. Nearly 90 people were wounded and several of them were in a serious condition on Monday after several explosive devices were thrown from crowds in front of the Ukrainian parliament building in Kiev, the interior minister said in a Tweet. (Photo by Valentyn Ogirenko/Reuters)

A couple dance tango for tourists at Caminito, a touristic hotspot of La Boca neighborhood in Buenos Aires, Argentina, October 15, 2016. (Photo by Enrique Marcarian/Reuters)

In this February 26, 1962 file photo, Mercury astronaut John Glenn, and his wife, Annie, ride in the back of an open car with Vice-President Johnson during a parade in Glenn's honor in Washington. The Capitol is seen in the background. Glenn, the first American to orbit Earth who later spent 24 years representing Ohio in the Senate, died Thursday, Dec. 8, 2016, at the age of 95. (Photo by AP Photo)

Jean-Pierre Giagnoli walks through a crowded area of vendors hawking cat related goods at CatCon LA in Los Angeles, on Sunday, June 26, 2016. (Photo by Richard Vogel/AP Photo)

A passenger not wearing pants sits in a subway train during the “No Pants Subway Ride” in Prague, Czech Republic, January 10, 2016. The event is an annual flash mob and occurs in different cities around the world in January, according to its organisers. (Photo by David W. Cerny/Reuters)

Camera trapper Xavier Hubert-Brierre put this large mirror on the side of a road through the jungle in Gabon and left a camera there to record how the animals would respond to their own reflections. A silverback gorilla thought it was seeing another silverback and responded by trying to scare off the potential challenger… (Photo by Xavier Hubert-Brierre/Johns Hopkins University Press)

The photography of Art Wolfe covers the globe, capturing landscapes, wildlife, and cultures from every continent; here he talks through a selection of his favourite images. Art Wolfe is an American photographer and conservationist. His photographs have been noted by environmental advocacy groups for their “stunning” visual impact. Here: Snowy owlets (Bubo scandiacus), Arctic National Wildlife Refuge, Alaska, USA. (Photo by Art Wolfe/Art Wolfe Stock)

An instructor (C) adjusts the posture of students of flight attendant major during a training session at Anhui Foreign Languages University, in Hefei, Anhui province, China, May 25, 2015. (Photo by Reuters/China Daily)