People clash with Venezuelan National Guards as they try to cross the border to Colombia over the Francisco de Paula Santander international bridge in Urena, Venezuela December 18, 2016. (Photo by Carlos Eduardo Ramirez/Reuters)

A large stainless steel shovel lies on top of steamed crabs at the A.E. Phillips & Son Inc. crab picking house on Hooper's Island in Fishing Creek, Maryland August 26, 2015. Workers speed through the lump and back fin meat inside the crabs while leaving the more tedious task of picking the claws to others. (Photo by Jonathan Ernst/Reuters)

The northern lights, or aurora borealis, appear in the sky over the Bamburgh lighthouse at Stag Rock in Northumberland, England on September 28, 2016. (Photo by Owen Humphreys/PA Wire via ZUMA Press)

A golden pheasant is seen at Hangzhou Safari Park in Hangzhou, Zhejiang Province, China, November 13, 2016. According to local media, the pheasant gains popularity as its golden feathers resemble the hairstyle of U.S. President-elect Donald Trump. (Photo by Reuters/Stringer)

Charcoal burner Zygmunt Furdygiel fires wood inside a charcoal furnace at a charcoal making site in the forest of Bieszczady Mountains, near the village of Baligrod, Poland October 27, 2016. (Photo by Kacper Pempel/Reuters)

This image made available by the Johns Hopkins University Applied Physics Laboratory on Wednesday, May 31, 2017 depicts NASA's Solar Probe Plus spacecraft approaching the sun. On Wednesday, NASA announced it will launch the probe in summer 2018 to explore the solar atmosphere. It will be subjected to brutal heat and radiation like no other man-made structure before. (Photo by Johns Hopkins University Applied Physics Laboratory via AP Photo)

Policemen detain topless activists of women's rights group Femen, who stage a performance during a protest against Ukrainian President Petro Poroshenko and the government while marking the Day of Dignity and Freedom near the presidential administration headquarters in Kiev, Ukraine November 21, 2017. (Photo by Valentyn Ogirenko/Reuters)

A Hong Kong Correctional Services Dog Unit (CSDU) officer demonstrates training at the CSDU training facility in Stanley, Hong Kong, China, 27 February 2018. The Hong Kong CSDU consists of 29 staff members divided across six dog teams. According to the department's latest figure from 2017, the average daily penal population of Hong Kong was 8,529. (Photo by Jérôme Favre/EPA/EFE)