Chinese President Xi Jinping holds a welcome ceremony for visiting Serbian President Tomislav Nikolic in Beijing, capital of China, March 30, 2017.

President Xi (C, front) walks with students as he attends a tree planting activity in Beijing, capital of China, March 29, 2017.

Former U.S. treasury secretaries Jacob Lew, Timothy Geithner, Robert Rubin and W. Michael Blumenthal (From R to L) attend the "Leader Speak: Treasury Secretaries" event at the China-US SkyClub in New York, on March 29, 2017.

Former South Korean President Park Geun-hye leaves the Seoul Central District Court in a car as she is transferred to a detention house in South Korea, on March 31, 2017.

Aerial photo taken on March 20, 2017 shows the view of Mar-a-lago club at Palm Beach, Florida, the United States.

U.S. space firm SpaceX made history on Thursday as it launched an already-used Falcon 9 rocket back into space for the first time and then landed its first stage on a droneship in the Atlantic Ocean.

Palestinian protesters burn tires near the Israeli fence during a protest to mark the Land Day in the West Bank town of Beit Jala near Bethlehem, March 30, 2017.

A model presents a creation designed by Wang Xiaoshi during China Fashion Show in Beijing, capital of China, March 30, 2017.

Ding Junhui of China competes during the 3rd round match against Mark Joyce of England at the 2017 World Snooker China Open Tournament in Beijing, capital of China, March 30, 2017. Ding won 5-3.

A ceremony paying homage to Huang Di, or Yellow Emperor, who is considered as the ancestor of all Chinese people, is held in Zhengzhou, capital of central China's Henan Province, March 30, 2017.