2 为什么有的补语用（in）doing sth 的形式，有的用to do sth的形式
上面be careful 的补语，肯定句为什么用in doing sth?否定句为什么用动词不定式(not ) to do sth?肯定句可以用be careful to do sth的形式吗?
为什么有的补语用（in）doing sth 的形式，有的用to do sth的形式?是固定用法还是有一定的规律? 又如：
have problems /trouble /difficulty (in ) doing sth
have fun (in ) doing sth
have a great time (in ) doing sth
be happy to do sth
最佳答案 2023-03-17 15:19
上面be careful 的补语，肯定句为什么用in doing sth?否定句为什么用动词不定式(not ) to do sth?肯定句可以用be careful to do sth的形式吗?
【答】英语的词语必须按照一定的要求搭配使用的，这个问题应该在词典中查阅 careful 这个词的例句和用法说明，最好查阅英英词典。be careful 后面的 not to do sth叫做动词不定式的否定式，不能叫做否定句。在be careful后面也可以接 to do sth的形式，不是只能接 not to do sth。如：Be careful to dispose of your litter properly. (《朗文当代高级英语辞典 》)
为什么有的补语用（in）doing sth 的形式，有的用to do sth的形式?是固定用法还是有一定的规律? 又如：
have problems /trouble /difficulty (in ) doing sth
have fun (in ) doing sth
have a great time (in ) doing sth
【答】以上的 (in ) doing sth都不是补语，而是状语。属于单词的习惯用法问题，可以在词典中有关的名词 problems /trouble /difficulty/fun/time 中查阅到例句和用法说明。
be happy to do sth
【答】be happy 后面的 to do sth叫做形容词的补足语，表示原因。
其它 1 个回答
【1】主语+be careful not to do sth 结构中，后面不定式“to do sth”作“目的状语”
You are careful not to wake the baby.
=In order not to wake the baby, you are careful.
你要注意以下不要吵醒了这个宝宝宝。
You are careful not to make mistakes.
=In order not to make mistakes, you are careful.
你要认真仔细不要犯错误。
You are careful not to lose the key.
=In order not to lose the key, you are careful.
你要当心不要丢掉这把钥匙。
【2】主语+be careful in doing sth 结构中，后面介词短语“in doing sth”作“方面状语”
We rely on them to be careful in doing experiments.
我们相信他们在作实验的时候是非常谨慎的。
You are very careful in answering these questions. 你在回答这些题目要非常小心。
You are careful in crossing the river.你过河要小心。
备注：如果去掉介词in可以理解为现在分词作时间状语。
You are very careful answering these questions.
=You are very careful while you are answering these questions.
当你你在回答这些题目的时候你要非常小心。
You are careful crossing the river.
=You are careful while you are crossing the river.
当你在过河时，你要要小心。
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