“Left behind” children Luo Hongni, 11 (L) and brother Luo Gan,10, carry flowers to be used as feed while doing chores in the fields on December 18, 2016 in Anshun, China. Like millions of Chinese children, the four Luo siblings are being raised by their grandparents in rural China as their parents left to find work in urban areas. (Photo by Kevin Frayer/Getty Images)

A woman carries earthen pots to fill them with drinking water on a hot summer day, on the outskirts of Ajmer, Rajasthan, India April 25, 2017. (Photo by Himanshu Sharma/Reuters)

Visitors pose for pictures under blooming cherry blossoms at a botanical garden in Nanjing, capital of China’s eastern Jiangsu province on March 15, 2019. (Photo by Reuters/China Stringer Network)

Women carry pitchers after filling them with water from a hand pump to their houses in Thane district in the western state of Maharashtra, India, May 30, 2019. (Photo by Francis Mascarenhas/Reuters)

Danielle Collins of the US reacts to a point in the first set while playing Caroline Wozniacki of Denmark during Round Two Women's Singles tennis match of the 2019 US Open at the USTA Billie Jean King National Tennis Center in New York on August 29, 2019. (Photo by Robert Deutsch/USA TODAY Sports)

Protesters begin to gather ahead of the UK Student Climate Network's Global Climate Strike at Millbank in London, England on September 20, 2019. (Photo by Gareth Fuller/PA Images via Getty Images)

A toddler dressed as Hindu Lord Krishna takes part in Krishna Janmashtami celebrations at a temple in Kolkata, India, on August 23, 2019. Krishna Janmashtami is an annual Hindu festival that celebrates the birth of Lord Krishna, the eighth avatar of Vishnu. (Photo by Tumpa Mondal/Xinhua News Agency)

A Kurdish fighter from the People's Protection Units (YPG) fires his rifle at Islamic State militants as he runs across a street in Raqqa, Syria, July 2017. (Photo by Goran Tomasevic/Reuters)