Two race pigs jump over an obstacle during a rural festivity in reference to Maria Ascension in San Bernardino, Switzerland on Monday, August 15 2016. (Photo by Samuel Golay/Keystone/TI-Press via AP Photo)

A colorful sky at sunset over the snowy mountains in Immenstadt, Bavaria, Germany, 20 November 2014. Cloudy weather is forecast in the region on 21 November. (Photo by Karl-Josef Hildenbrand/EPA)

The sun rises over the River Brue on the Somerset Levels as temperatures in parts of the south west drop below freezing, on January, 20, 2015. (Photo by Ben Birchall/PA Wire)

A police officer lies on the street after being run over by a bus during a protest against the increase in the price of public transport in San Cristobal, Venezuela March 29, 2016. (Photo by Carlos Eduardo Ramirez/Reuters)

An Afghan National Army (ANA) helicopter flies over a soldier during a training exercise at the Kabul Military Training Centre in Afghanistan October 7, 2015. (Photo by Ahmad Masood/Reuters)

A massive sand storm cloud is close to enveloping a military camp as it rolls over Al Asad, Iraq, April 27, 2005. (Photo by Cpl. Alicia M. Garcia, U.S. Marine Corps/Reuters/U.S. Department of Defense)

Gun enthusiasts look over Smith & Wesson pistols at the NRA Annual Meetings & Exhibits on May 21, 2016 in Louisville, Kentucky. About 80,000 visitors are expected to attend the three-day event. (Photo by Scott Olson/Getty Images)

In this Wednesday, September 17, 2014 photo, the sun shines over a field of sunflowers in Walkill, N.Y. (Photo by John DeSanto/AP Photo/Times Herlad-Record)