常用结构:It+be+ adj./n.+ for sb. to dosth. (常见形容词: difficult , important, necessary, impossible, etc.) It+be+adj. + of sb. to do sth. =sb. be + adj. + to do sth. (常见形容词:clever, silly, foolish, stupid, wise, kind, rude, impolite,careless, ...
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