Tour guides wearing traditional Chinese dress practice smiling by biting chopsticks at Qingming Grand-River Park in Kaifeng, central China's Henan Province on March 2, 2017, aiming to provide better service for visitors. (Photo by IPA Asia via ZUMA Wire)

A Romanian female soldier adjusts her helmet before taking part in weapons training with US Marines female counterparts at the Capu Midia Surface to Air Firing Range, on the Black Sea coast in Romania, Monday, March 20, 2017. About 1,200 US and Romanian troops take part in the Spring Storm 17 exercise, meant to simulate defense of the Romanian Black Sea coastline and urban areas. (Photo by Vadim Ghirda/AP Photo)

A bride gets her make-up done before the start of a mass marriage ceremony in Kolkata, India, February 14, 2016. A total of 150 tribal Hindu, Muslim and Christian couples from various villages across the state took their wedding vows on Sunday during the day-long mass marriage ceremony organised by a social organisation, the organisers said. (Photo by Rupak De Chowdhuri/Reuters)

In this photo taken on Wednesday, February 17, 2016, a volunteer fighter with the Syrian Government forces sits atop a tank in the province of Raqqa, Syria. In recent weeks, Syrian government forces captured dozens of villages and towns across the country. (Photo by Alexander Kots/Komsomolskaya Pravda via AP Photo)

A child coughs as migrants and refugees run away after Macedonian police fired tear gas at hundreds of Iraqi and Syrian migrants who tried to break through the Greek border fence in Idomeni, on February 29, 2016. Greek police said more than 6,000 people were massed at the border, in a buildup triggered by Austria and Balkan states capping the numbers of migrants entering their territory. (Photo by Louisa Gouliamaki/AFP Photo)

UFC women's bantamweight champion Holly Holm and Miesha Tate face off during the UFC 196 weigh ins at the MGM Grand Garden Arena in Las Vegas on Friday, March 4, 2016. (Photo by L.E. Baskow/Las Vegas Sun via AP Photo)

Marieke van der Meer from the Netherlands works on her sculpture “Flora” at the sand sculpture show in Binz on Ruegen island, Germany, 09 March 2016. With the motto “Fascination Nature”, 50 sand artists have created oversized sculptures. The sculptors use 16,000 tons of special sand that is pressed into big blocks first and then formed. The 7th sand sculpture show on 5,600 square meters of exhibition ground opens on 12 March 2016. (Photo by Ens Buettner/EPA)

A couple stands next to a poster depicting Dutch politician Geert Wilders and Russian President Vladimir Putin kissing, at a metro station in Amsterdam April 3, 2016. (Photo by Cris Toala Olivares/Reuters)