A man smiles as he carries firewood he bought on a street amid ongoing fuel and cooking gas shortages in Yemen's capital Sanaa December 2, 2015. (Photo by Khaled Abdullah/Reuters)

A tribesman loyal to the Houthi movement carries his rifle as he leaves a gathering held to show support for the group, in Yemen's capital Sanaa December 15, 2015. (Photo by Khaled Abdullah/Reuters)

Refugees disembark and make their way to a camp at a hotel touted as the world's most northerly ski resort in Riksgransen, Sweden, December 15, 2015. (Photo by Ints Kalnins/Reuters)

People hold out money as butchers sell their remaining produce of the year at discounted prices during the traditional Christmas Eve auction at Smithfield's market in London December 24, 2015. (Photo by Neil Hall/Reuters)

Photographers help a Rohingya refugee to climb out of Naf River as they cross the Myanmar-Bangladesh border in Palong Khali, near Cox's Bazar, Bangladesh on November 1, 2017. (Photo by Hannah McKay/Reuters)

A golden pheasant and squirrels are seen in Lushan County of Pingdingshan City, central China's Henan Province, November 14, 2017. (Photo by Liu Xianguo/Xinhua/Barcroft Images)

Golden monkeys play at a conservation base in Shennongjia, central China's Hubei Province, January 26, 2018. The golden monkey conservation base witnessed a snowfall recently. (Photo by Du Huaju/Xinhua/Barcroft Images)

Athlets run during the women's 3000 meter steeplechase at the International Athletics Meeting in Lucerne, Switzerland, 14 June 2016. (Photo by Alexandra Wey/EPA)