In this photo taken on Monday, January 5, 2015, a mallard duck attempts to walk on a frozen pond in Yukon, Okla. (Photo by Steve Gooch/AP Photo/The Oklahoman)

Protesters wear masks, the left in the colors of the Kenyan national flag, as they join others carrying mock coffins and red-painted crosses, symbolizing the blood of the 28 non-Muslims singled out and killed in the recent attack on a bus in Mandera by Somali militant group al-Shabab, outside government offices in downtown Nairobi, Kenya Tuesday, November 25, 2014. (Photo by Ben Curtis/AP Photo)

“Warming up”. This photo I capture in the early afternoon, the animal species of lemurs fly. Photo location: Sambas, West Kalimantan, Indonesia. (Photo and caption by Hendy Mp/National Geographic Photo Contest)

Cuban-American artist Jorge Rodriguez-Gerada's six-acre sand and soil “facescape” stretches across the JFK Hockey Field on the north side of the Reflecting Pool along the National Mall October 1, 2014 in Washington, DC. Titled “Out of Many, One” and composed of 2,500 tons of sand, 800 tons of top soil and eight miles of string, the piece is the artist's interpreative blending of 30 different men's faces. Rodriguez-Gereda used high-precision global positioning satellites to place 10,000 wood pegs as waypoints for the giant face. The piece will be open to the public beginning October 4 and will eventually be tilled back into the earth. (Photo by Chip Somodevilla/Getty Images)

Belgium. Rosalie, 9, goes to school in Brussels. “At my school we have separate toilets for girls and boys on every floor. My classroom is on the 3rd floor. We have 22 toilets, which are shared between 230 pupils and 20 adults. The teachers at school let us go to the toilet whenever we need to”. (Photo by Tim Dirven/WSUP/Panos)

Seen in a long exposure nighttime photograph, a burned van rests in a lot while a wildfire glows on the horizon in Phelan, Calif., early Thursday, August 18, 2016 2016. (Photo by Noah Berger/AP Photo)

A man impersonating Kim Jong-un gestures during the athletics at the Rio 2016 Olympic Games at the Olympic Stadium in Rio de Janeiro on August 18, 2016. (Photo by Johannes Eisele/AFP Photo)

A girl washes the body paint off her arm on the shore of Lake Balaton during the coinciding Strand Festival and B.My.Lake Festival in Zamardi, 110 kms southwest of Budapest, Hungary, 24 August 2016. (Photo by Zoltan Balogh/EPA)