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1. Dentists always ask questions when it is impossible for you to answer.
牙科医生们总是在你无法作出回答的时候向你提出问题。
It is + adj.+ for sb. to do sth 句型
这里it是形式主语，真正的主语是to answer。
It is+adj+that +句子
对他来说帮助你是不可能的
It is impossible for him to help you. = It is impossible that he will help you.
My dentist had just pulled out one of my teeth and had told me to rest for a while.
我的牙科医生刚刚给我拔掉了一颗牙，叫我休息一会儿。
pull vt.&vi.拉，拖，牵，扯反义词 ←→push vt.推我感觉有人拉着我的胳膊。
I felt someone pulling my arm. You are pulling my leg.
pull one's leg 开某人玩 笑
pull out ----拔出 rest v.休息
for a while,一会儿，片刻。
3. l tried to say something, but my mouth was full of cotton wool.
我想说点什么，但我嘴里塞满了药棉。
cotton wool本意是指“原棉”的意思，也就是棉花最初的状态。在英国英语中，多用来指代“药棉”。
try to do 努力，尽力做某事(未必会成功)
manage to do 尽力做某事一定会成功
try doing 试着做某事
be full of = be filled with
But my mouth was filled with cotton wool.他的钱包里装满了钱
The wallet is full of money
The wallet is filled with money
