Couples take part in a competition during a mass wedding of 64 doctoral student couples at Harbin Institute of Technology, a university in Harbin, Heilongjiang province, China, June 4, 2017. (Photo by Reuters/Stringer)

A military police officer aims his gun to a demonstrator during a protest in Brasilia, Brazil, Tuesday, April 7, 2015. The officer had picked up a bottle that was thrown towards them but did not fire his gun and backed away. Thousands of workers have staged rallies in 12 cities across Brazil to protest against a proposed law that would allow companies to outsource their labor force. (Photo by Eraldo Peres/AP Photo)

Ratana Das, 40, a female vendor, carries sacks full of clothes at a second-hand clothing market early morning in Kolkata, India, March 10, 2016. Das said she was born and brought up in Kolkata and feels proud being a resident of the city that gives her he opportunity to be financially independent. (Photo by Rupak De Chowdhuri/Reuters)

An Afghan man works at a traditional yarn factory in Heart province, Afghanistan July 28, 2015. (Photo by Mohammad Shoib/Reuters)

Ary Borges feeds his tiger named Dan at his home in Maringa, Brazil, Thursday, September 26, 2013. Borges is in a legal battle with federal wildlife officials to keep his endangered animals from undergoing vasectomies and being taken away from him. He defends his right to breed the animals and says he gives them a better home than they might find elsewhere in Brazil. (Photo by Renata Brito/AP Photo)

A Pakistani feeds his goat wearing the words “Eid Mubarak” or “Eid Greeting”, to be slaughtered on the Muslim holiday of Eid al-Adha, or “Feast of Sacrifice”, in Islamabad, Pakistan on Tuesday, October 15, 2013. Muslims all over the world are celebrating Eid al-Adha by sacrificing sheep, goats, cows and camels, to commemorate the Prophet Abraham's readiness to sacrifice his son, Ismail, on God's command. (Photo by Anjum Naveed/AP Photo)

Members of the Dominican Armed Forces participate in a commemorative act on the 170th anniversary of national independence at the esplanade of Santo Domingo, on February 27, 2014. (Photo by Orlando Barria/EPA)

An instructor (C) adjusts the posture of students of flight attendant major during a training session at Anhui Foreign Languages University, in Hefei, Anhui province, China, May 25, 2015. (Photo by Reuters/China Daily)