(L-R) U.S. President Barack Obama, Queen Elizabeth II and First Lady Michelle Obama arrive at Winfield House, the residence of the Ambassador of the United States of America, in Regent's Park, on May 25, 2011 in London, England. The 44th President of the United States, Barack Obama, and First Lady Michelle are in the UK for a two day State Visit at the invitation of HM Queen Elizabeth II. Last night they attended a state banquet at Buckingham Palace and today's events include talks at Downing Street and the President will address both houses of Parliament at Westminster Hall. (Photo by Yui Mok - WPA Pool/Getty Images)

“Kilauea Rules”. The most extreme place we put ours kayakers to paddle till now. Photo location: Big Island, Hawaii. (Photo and caption by Alexandre Socci/National Geographic Photo Contest)

Stuart Craig of Washington tries out a Sig Sauer 1911 model Scorpion pistol at the Sig Sauer booth at the National Shooting Sports Foundation's 34th annual Shooting, Hunting, Outdoor Trade (SHOT) Show at the Sands Expo and Convention Center January 17, 2012 in Las Vegas, Nevada. The SHOT Show is the largest annual gathering of shooting professionals with more than 1,600 exhibitors and 30,000 attendees expected. (Photo by Ethan Miller/Getty Images)

In this March 18, 2015 photo, Andrea, better known as Loira, which is the Portuguese word for “blonde”, poses for a portrait in an open-air crack cocaine market, known as a “cracolandia” or crackland where users can buy crack, and smoke it in plain sight, day or night, in Rio de Janeiro, Brazil. Andrea says she is married and has a home, but she keeps returning to crackland to feed her addiction. (Photo by Felipe Dana/AP Photo)

A man yells for help minutes after a Serb shell hit a crowded pedestrian walkway in Sarajevo, May 1993. Radovan Karadzic, a 70-year-old former psychiatrist, still in robust health, is the most senior political figure to be convicted by the International Criminal Tribunal for the Former Yugoslavia. He was found guilty of 10 out of 11 charges. He was acquitted of a second count of genocide in Bosnian towns. (Photo by Reuters)

Lindsey Vonn of USA wins the bronze medal during the FIS World Ski Championships Women's Downhill on February 10, 2019 in Are Sweden. (Photo by Leonhard Foeger/Reuters)

Nature, singles winner: Frogs with their legs severed struggle to the surface, surrounded by frogspawn, after being thrown back into the water in Covasna, Romania. (Photo by Bence Mate/World Press Photo 2019)

Daniel Cheong, a dog behaviorist and trainer, steps over a leash as he walks a pack of dogs in Arlington, Va. on November 13, 2018. (Photo by Ricky Carioti/The Washington Post)