Chinese President Hu Jintao called for an immediate cease-fire in Libya an even worse humanitarian crisis in the country at the BRICS Summit in Hainan Province.
A. to prevent
B. to have prevented
C. preventing
D. having prevented
网友回答
(答案→)A. to prevent
B. to have prevented
C. preventing
D. having prevented
解析：本题考查非谓语动词。to prevent用不定式表示目的性，to have prevented表示动作已经完成。所以选A。