这是个固定句型主语+ be+ 形容词+ to do(主动式,因为句子的主语是不定式的逻辑宾语）再如：The question is easy to answerThe sentence is difficult to translate.The apple is good to eat.The math problem is e...可是问题不是被解决吗，不就应该用to be solved吗，solved也可以表示被动，为什么不能用啊？我说了， 此句型中的主语是不定式的逻辑宾语！！！你看：The problem is easy to solve.=It is easy to solve the problem.