A worker walks through a salt pan on the eve of May Day or Labour Day on the outskirts of the southern Indian city of Chennai April 30, 2014. India is the third largest salt producing country in the world after China and U.S. with global annual production about 230 million tonnes, according to government data. (Photo by Reuters/Babu)

Lightning illuminates a thundercloud as a storm front hits the North Sea region near Westerhever, northern Germany, on August 11, 2014. (Photo by Daniel Reinhardt/AFP Photo/DPA)

Gold medallists of China perform Synchronised Swimming Free Combination routine at the Munhak Park Tae-hwan Aquatics Center during the 17th Asian Games in Incheon September 23, 2014. (Photo by Tim Wimborne/Reuters)

A small section of the expanding remains of the Veil Nebula, a massive star that exploded about 8,000 years ago. The entire nebula is 110 light-years across, covering six full moons on the sky as seen from Earth, and resides about 2,100 light-years away in the constellation Cygnus, the Swan. (Photo by Reuters/NASA/ESA/Hubble)

An empty cell block is pictured within Joint Task Force Guantanamo's Camp VI at the U.S. Naval Base in Guantanamo Bay, Cuba March 22, 2016. (Photo by Lucas Jackson/Reuters)

Ammunition airlift into besieged Khe Sanh, Operation Pegasus, April 1968. (Photo by Larry Burrows/AP Photo)

People dressed as a dancing devils with giant mask dance on a street, during a traditional celebration in Naiguata, Venezuela, Thursday, May 31, 2018. Carrying in their hands striking masks mostly animals and sea monsters, hundreds of men, women and children went out to dance frantically as possessed by evil spirits in an ancient ritual known as Dancing Devils of Naiguata, the unorthodox way of the coastal towns of Venezuela to venerate God during the celebrations of Corpus Christi. (Photo by Ariana Cubillos/AP Photo)

Two Girls who managed to evade the police walk away as police on foot and horseback push back to te curd at Park Row, In New York on April 26, 1960, A milling throng of more than 1,000 High students who storned city hall in a Demonstration supporting teachers wage demands. (Photo by AP Photo)