it is a good idea to have a rest这里为什么用to?答:A)it is+ 形容词+of sb.+ to do sth. ==sb.+ be+形容词+to do sth.该句型中形容词用来描述不定式行为者的性格、品行等,形容词多为brave, careless, clever, polite, wrong, kind, good, nice, foolish, rude (粗鲁的), selfish(自私的)等。如:It’s very kind of you to say so...