An undercover police officer, who had been marching with anti-police demonstrators, aims his gun at protesters after some in the crowd attacked him and his partner in Oakland, California December 10, 2014. Police said more than 100 demonstrators marched in Berkeley, California, which has a history of social activism. Under cloudy skies, turnout was smaller than earlier in the week, when demonstrators in the area threw rocks at police and shut down a major freeway. (Photo by Noah Berger/Reuters)

A girl dances in front of the digital art installation “Light in Dark” created by teamLab, a collaborative of Japanese digital artists, during a special exhibition of “Shake! Art Exhibition! and Learn and Play! teamLab Future Park” at National Museum of Emerging Science and Innovation (or Miraikan) in Tokyo, Japan, 19 January 2015. The exhibition is held through 01 March 2015. (Photo by Kimimasa Mayama/EPA)

Young gymnasts practice pull-up on a bar at a gymnasium of a sports school in Jiaxing, Zhejiang province April 11, 2015. (Photo by William Hong/Reuters)

A student, wearing a traditional costume and headdress, stands in line for interviews during a recruitment held by an airline company, hoping to stand out from more than 500 candidates for airline stewardess positions, in Chengdu, Sichuan Province, China, May 27, 2016. (Photo by Reuters/Stringer)

NYC no pants subway ride. Thousands of straphangers took their pants off for the 15th annual "No Pants Subway Ride" hosted by Improv Everywhere. People gathered at seven meeting points throughout the five boroughs at 3PM. All participants met up at Union Square around 5PM to and had a pant-less celebration and the afterparty at Webster Hall. (Photo by Paul Martinka/The New York Post)

In this January 7, 2016, photo, conservationists of Borneo Orangutan Survival Foundation hold a baby orangutan rescued along with its mother during a rescue and release operation for orangutans trapped in a swath of jungle in Sungai Mangkutub, Central Kalimantan, Indonesia. Last year's forest fires drove orangutans closer to the river bank, where they had to live in an over-populated swath of forest as thin as 30 meters wide along the river. (Photo by Dita Alangkara/AP Photo)

A man rides a motorcycle along a street in the snow in Altay, Xinjiang Uighur Autonomous region, February 9, 2016. (Photo by Reuters/Stringer)