An Afghan boy jumps off the turret of a Soviet tank on a hilltop on the the outskirts of Kabul, Sunday, March, 4, 2018. (Photo by Rahmat Gul/AP Photo)

South Vietnamese forces escort suspected Viet Cong officer Nguyen Van Lem (also known as Bay Lop) on a Saigon street February 1, 1968, early in the Tet Offensive. Moments later, Lem was executed by Gen. Nguyen Ngoc Loan, chief of the national police. (Photo by Eddie Adams/AP Photo)

A thirsty timber wolf, Lithuania, 2018. (Photo by Erikas Plucas/Alamy Stock Photo)

A pilot inflates a hot air balloon while taking part in the 38th International Balloon Festival of Chateau-d'oex, Switzerland, 23 January 2016. The festival takes place from 23 to 31 January. (Photo by Vincent Vannay/EPA)

People sit next to a pool where the Tower of Madrid skyscraper is reflected at sunset in Madrid, Thursday, November 26, 2015. The tower was the tallest in Spain since it was finished in 1957 until 1982. (Photo by Francisco Seco/AP Photo)

The sun rises beside St Mary's Lighthouse in Whitley Bay, Tyne and Wear, as the unseasonably cool weather continues on Thursday, April 28, 2016. (Photo by Owen Humphreys/PA Wire)

Two white storks stand close to each other on their nest on a tree in Zerbolo, Italy, Thursday, October 26, 2017. (Photo by Antonio Calanni/AP Photo)

A pine marten – one of a few wild mammals doing well in Britain (although they number just 3,700). A fifth of the country’s wild mammals are at high risk of extinction, research shows. (Photo by Maurice Flynn/The Mammal Society)