A young arab boy, armed with a rifle and a knife, in the Aden Protectorate near Yemen. (Photo by Richards/Fox Photos/Getty Images). February 1938

Residents watch the ocean waves crash into the water front, after the passage of Hurricane Irma, in Cuba, Sunday, September 10, 2017. (Photo by Ramon Espinosa/AP Photo)

Drummers perform during rehearsals at the Bird's Nest National Stadium ahead of the IAAF Athletics World Championships in Beijing on August 20, 2015. The Athletics World Championships will be held at the stadium from August 22 to 30. (Photo by Greg Baker/AFP Photo)

Finding just the right spot above the clouds at Camp 1 on Ama Dablam, Danuru Sherpa uses his iPhone to catch up with friends and family. Even at 18,500 feet (5,654 meters), climbers here can check their email and other dispatches from the world below. (Photo by Aaron Huey/National Geographic)

An armed man herds his cattle close to the village of Nimini in northern South Sudan, February 8, 2017. In the chaos of South Sudan's civil war, it took three years for Nyagonga Machul to find her lost children. Machul had traveled from her village to the capital when President Salva Kiir, an ethnic Dinka, fired his deputy Riek Machar, a Nuer, in 2013. (Photo by Siegfried Modola/Reuters)

A six-year-old acrobat performs on the opening of a tourist festival in Bozhou, Anhui province, China May 3, 2015. (Photo by Reuters/China Daily)

Cars float up from a car garage in a mixture of storm water and gasoline in lower Manhattan as workers begin the process of pumping out the mess. (Photo by Carolyn Cole/Los Angeles Times/MCT)

A woman and a child walk past the remains of collapsed houses damaged during the April 2015 earthquake, in Bhaktapur, Nepal March 18, 2016. The two devastating earthquakes that struck Nepal last year killed almost 9,000 people across the country. Inside the Kathmandu Valley almost 2,000 died, and some of the area's most important cultural and heritage sites were completely destroyed. As Kathmandu inhabitants prepare to mark the one-year anniversary of the event, thousands are still displaced and millions are living in temporary shelters. (Photo by Navesh Chitrakar/Reuters)