第12题: [单项选择]The pressure ______ causes American to be energetic, but it also puts them trader a constant emotional strain. A. to compete B. competing C. to be competed D. having competed 参考答案:A 答案解析:[解析] 动词不定式作定语时,不定式置于被修饰的名词之后。A项与C项的差别在于语态,compete属不及物动词,不能构成被动形式。