Opposition students march against Venezuelan President Nicolas Maduro's government in Caracas February 12, 2015. Venezuelan troops blocked students during marches against Maduro on Thursday as pro-government supporters also rallied on the anniversary of 2014 protests that led to 43 deaths. In Caracas, troops cordoned off scores of students on an unauthorized march to a church where they planned a mass in honour of demonstrators who died. (Photo by Jorge Silva/Reuters)

A woman dancing on the Sphinx. A pyramid can be seen in the background. (Photo by Fox Photos/Getty Images). 1928

Two men using an electric power saw to fell a tree circa 1940's. (Photo by Keystone View/FPG/Getty Images)

Undated handout issued by Take A View of Sunrise at Winnats Pass, Derbyshire, England which won the Visit Britian “You're invited” Award for the best image from an overseas entrant category in this year's Landscape Photographer of the Year Awards. (Photo by Sven Mueller/PA Wire)

A Philippine boy collects used plastic bottles to be sold at a junk shop at Divisoria market in Manila on November 29, 2017. (Photo by Noel Celis/AFP Photo)

Employees stand near an airframe for the second Antonov-225 Mriya plane at Antonov aircraft plant in Kiev, Ukraine, September 7, 2016. Ukraine hopes to attract $500 million of investment from China to complete an updated version of the world's biggest aircraft, the Antonov-225 Mriya, the president of manufacturer Antonov said on Wednesday. (Photo by Valentyn Ogirenko/Reuters)

A woman looks out from her stall selling traditional garments and textiles at a market in Ashgabat February 8, 2012. (Photo by Aman Mehinli/Reuters)

Pakistani children cool themselves off in a stream in Peshawar, Pakistan, Monday, June 29, 2015, during Muslim's fasting month of Ramadan. (Photo by Mohammad Sajjad/AP Photo)