to understand the problem is very difficult.(用it作为形式主语）—— ——very difficult____ underst
问题描述：
to understand the problem is very difficult.(用it作为形式主语）—— ——very difficult____ underst
答
to understand the problem is very difficult.(用it作为形式主语）—— ——very difficult____ understIt is very difficult to understand the problem 形式主语：It系动词：is 表语：very difficult 动词不定式...