They were able to prevent SARS ________ by ________ the patients．
A.to spread…isolateB.spreading…isolatingC.from spreading…isolateD.having spread…isolating在线课程B
动词prevent的用法是prevent sb from doing sth意思是“阻止／妨碍某人做某事（在这个词组中的介词from可以省略）”。prevent sb by doing sth意思是“通过某种手段阻止某人做某事”。