In this Saturday, March 21, 2015 photo, a porter rests carrying supplies for the upcoming climbing season, near the Everest Base camp, Nepal. Nepal has cleared more than 300 mountaineers to climb Mount Everest after they had to abandon last year's efforts when an ice avalanche killed 16 guides in the mountain's deadliest disaster, an official said on March 20. The three-month climbing season for Everest, the world's tallest mountain, begins in March. (Photo by Tashi Sherpa/AP Photo)

Competitors climb in front of the Matterhorn mountain at the start of the 21st Glacier Patrol race in Stafel outside the ski resort of Zermatt, Switzerland, 18 April 2018. The Glacier Patrol (Patrouille des Glaciers in French), organized by the Swiss Army, takes place from April 17 to 21. Highly-experienced hiker-skiers trek for over 53km (3994m ascent and 4090m descent) along the Haute Route along the Swiss-Italian border from Zermatt to Verbier. (Photo by Valentin Flauraud/EPA/EFE)

Danusorn Sdisaithaworn, 10, poses for a portrait during an annual Poy Sang Long celebration, a traditional rite of passage for boys to be initiated as Buddhist novices, while he visits a relative's house outside Mae Hong Son, Thailand, April 4, 2018. (Photo by Jorge Silva/Reuters)

Fifty years ago, as France exploded in mass protests, words scrawled on the walls of the Sorbonne summed up the revolutionary zeal of the time: “Run free, comrade, we’ve left the old world behind!”. Sexual liberation, artistic creativity and anti-capitalism were the order of the day. For those who were there, it was an unforgettable time. Here: A wounded student is transported by first-aid workers during riots on the Boulevard Saint-Michel, Paris, France on May 6, 1968. (Photo by Gökşin Sipahioğlu/SIPA Press)

Cha Huilan, a 40-year old Lisu woman, and her daughter leave Lazimi village with a zipline across the Nu River in Nujiang Lisu Autonomous Prefecture in Yunnan province, China, March 24, 2018. Chinese mountain villagers, cut off from shops and churches by a raging river, use a zipline to cross its violent rapids and jagged rocks. (Photo by Aly Song/Reuters)

Democratic Congressional candidate Alexandria Ocasio-Cortez poses with a campaign worker during a whistle stop in Queens, New York, November 5, 2018. (Photo by Andrew Kelly/Reuters)

Workers pull apart a house in Khandyga, Russia, on February 2, 2018. The shifting ground caused by the uneven thawing of permafrost each summer causes buildings like this Soviet-era apartment house to sag and collapse. (Photo by Amos Chapple/Radio Free Europe/Radio Liberty)