题目内容
12．
necessary，do．It is necessary to do exercise．．
分析 锻炼是必要的．
解答 答案：It is necessary to do exercise．图片上是一些人在做锻炼，necessary是形容词"必要的"，故造句每天锻炼是必要的．是在说客观事实用一般现在时，用句型it's+adj+to do sth，it是形式主语，动词不定式是真正主语，do exercise做锻炼．故答案是It is necessary to do exercise．
点评 it's+adj．+for sb．to do sth．结构是一个陈述句，表示说话人对客观事件的决断，比较正式，希望大家学习时注意． 若形容词是描述不定式行为者的性格、品质的，如kind，good，nice，right，wrong，clever，careless，polite，foolish等，用of sb．．
It's very kind of you to help me．你能帮我，真好．
It's clever of you to work out the maths problem．你真聪明，解出了这道数学题．
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