In pics: 2017 U.S. Open on day 7

Petra Kvitova of Czech Republic serves to Garbine Muguruza of Spain during the women's singles fourth round match at the 2017 U.S. Open in New York, the United States, Sept. 3, 2017. Petra Kvitova won 2-0 to enter the next round. (Xinhua/Qin Lang)