Then U.S. Army First Lieutenant Kirsten Griest (C) and fellow soldiers participate in combatives training during the Ranger Course on Fort Benning, Georgia, in this handout photograph taken on April 20, 2015 and obtained on August 20, 2015. When Griest and another woman completed the daunting U.S. Army Ranger school this week they helped end questions about whether women can serve as combat leaders, as the Pentagon is poised to open new roles, including elite Navy SEALs, to women in coming months. The feat by Griest and First Lieutenant Shaye Haver followed a re-evaluation of the role of women after their frontline involvement in Iraq and Afghanistan and the end of a rule barring them from combat roles in 2013. (Photo by Spc. Nikayla Shodeen/Reuters/U.S. Army)

A visitor kneels on the 180-meter-high and 300 meter-long glass-bottomed suspension bridge at the Shiniuzhai National Geopark in Pingjiang county, in central China's Hunan province, 24 September 2015. (Photo by Jiao Zi/Imaginechina via AFP Photo)

The view at night from the Shanghai Tower in Shanghai, China on August 7, 2015. The tower is technically smaller than the Burj Khalifa in Dubai but, while the observation deck of Dubai’s mega-structure is at 556m, the Shanghai Tower’s is at 561m, meaning the view is a little higher. (Photo by Paul Reiffer/REX Shutterstock)

Tajammu Al-Ezza brigade fighters react while firing a Grad shell towards forces of Syria's President Bashar Al-Assad stationed in Salhab village, Hama countryside, May 7, 2015. (Photo by Mohamad Bayoush/Reuters)

Eva Longoria Farmer Visits "The Tonight Show Starring Jimmy Fallon" at Rockefeller Center on November 24, 2015 in New York City. (Photo by Theo Wargo/NBC/Getty Images for "The Tonight Show Starring Jimmy Fallon")

Public Space series, 2015. This series by Morteza Niknahad and Behnam Zakeri tends toward cinema, taking an almost cartoonish view of modern life in Iran. This work was inspired by the social life of dolphins. (Photo by Morteza Niknahad and Behnam Zakeri/The Guardian)

A flock of starlings is seen as they perform their traditional dance fly before landing to sleep during the sunset near the southern Arab Israeli city of Rahat, in the northern Israeli Negev desert, on February 2, 2015. (Photo by Menahem Kahana/AFP Photo)

(L-R) Leigh-Anne Pinnock, Jesy Nelson, Perrie Edwards and Jade Thirlwall of Little Mix attend the KISS FM Haunted House Party at SSE Arena on October 29, 2015 in London, England. (Photo by Dave J. Hogan/Dave J. Hogan/Getty Images)