干吗不……?"。例如：
Why not take a holiday? 干吗不去度假?
7.14 不定式的时态和语态
1） 一般式表示的动词，有时与谓语动词表示的动作同时发生，有时发生在谓语动词的动作之后，例如
He seems to know this. 他似乎知道这事。
I hope to see you again. = I hope that I'll see you again. 我希望再见到你。
2） 完成式表示的动作发生在谓语动词表示的动作之前。例如：
I'm sorry to have given you so much trouble. 很抱歉，给你添了那么多的麻烦。
He seems to have caught a cold. 他好像已经得了感冒。
3） 进行式表示动作正在进行，与谓语动词表示的动作同时发生。例如：
He seems to be eating something. 他好像正在吃什么东西。
4） 完成进行式表示动作从过去开始并延续至说话的时候。例如：
She is known to have been working on the problem for many years. 我们知道她研究这问题有好几年了。
7.15 动名词与不定式
1）动名词与不定式的区别：
动名词表达的是： 状态，性质，心境，抽象，经常性，已发生的
不定式表达的是： 目的，结果，原因，具体，一次性，将发生的
2）有些动词如continue接不定式或动名词作宾语，意义基本相同。
3）有些动词如continue接不定式或动名词作宾语，意义大相径庭。常见的，下一节有专门讨论。
８.特殊词精讲
8.1 stop doing/to do
stop to do 停止，中断做某事后去做另一件事，stop doing 停止做某事。例如：
They stop to smoke a cigarette. 他们停下来，抽了根烟。
I must stop smoking. 我必须戒烟了。
典型例题：
She reached the top of the hill and stopped ___ on a big rock by the side of the path.
A. to have rested B. resting C. to rest D. rest
答案：C。由题意可知，她到了山顶，停下来在一个路边的大石头上休息。因此，应选择"stop to do sth. 停下来去做另一件事"。而不仅仅是爬山动作的终止，所以stop doing sth.不正确。
8.2 forget doing/to do
forget to do 忘记要去做某事，forget doing 忘记做过某事。例如：
The light in the office is stil on. He forgot to turn it off. 办公室的灯还在亮着，他忘记关了。（没有做关灯的动作）
He forgot turning the light off. 他忘记他已经关了灯了。（已做过关灯的动作）
典型例题：
---- The light in the office is still on.
---- Oh，I forgot___.
A. turning it off B. turn it off C. to turn it off D. having turned it off
答案：C。由the light is still on 可知灯亮着，即关灯的动作没有发生，因此用forget to do sth.而forget doing sth表示灯已经关上了，而忘记了这一事实。此处不符合题意。
8.3 remember doing/to do
remember to do 记得去做某事，remember doing 记得做过某事。例如：
Remember to go to the post office after school. 记着放学后去趟邮局。
Don't you remember seeing the man before? 你不记得以前见过那个人吗?
8.4 regret doing/to do
regret to do 对将要做的事遗憾，regret doing 对做过的事遗憾、后悔。例如：
I regret to have to do this, but I have no choice. 我很遗憾必须这样去做，我实在没有办法。
I don't regret telling her what I thought. 我不为告诉她我的想法而后悔。
典型例题：
---You were brave enough to raise objections at the meeting.
---Well, now I regret ___ that.
A. to do B. to be doing C. to have done D. having done
答案：D。regret having done sth. 对已发生的事感到遗憾。regret to do sth. 对将要做的事感到遗憾。本题为对已说的话感到后悔，因此选D。
8.5 cease doing/to do
cease to do 长时间，甚至永远停做某事，cease doing 短时停止做某事，以后还会接着做。例如：
That department has ceased to exist forever. 那个系已不复存在。
The girls ceased chatting for a moment when their teacher passed by. 姑娘们在老师走过时，停了会聊天。
8.6 try doing/to do
try to do 努力，企图做某事，try doing 试验，试着做某事。例如：
You must try to be more careful. 你可要多加小心。
I tried gardening but didn't succeed. 我试着种果木花卉，但未成功。
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8.7 go on doing/to do
go on to do 做了一件事后，接着做另一件事，go on doing 继续做原来做的事。例如：
After he had finished his maths，he went on to do his physics. 做完数学后，他接着去做物理。
Go on doing the other exercise after you have finished this one. 作完这个练习后，接着做其他的练习
8.8 be afraid doing/to do
be afraid to do 不敢，胆怯去做某事，是主观上的原因不去做，意为"怕"，be afraid of doing 担心出现doing的状况、结果。doing 是客观上造成的，意为"生怕，恐怕"。例如：
She was afraid to step further in grass because she was afraid of being bitten by a snake.
她生怕被蛇咬着，不敢在草丛中再走一步。
She was afraid to wake her husband. 她不敢去叫醒她丈夫。
She was afraid of waking her husband. 她生怕吵醒她丈夫。
8.9 be interested doing/to do
interested to do 对做某事感兴趣，想了解某事，interested in doing 对某种想法感兴趣，doing 通常为想法。例如：
I shall be interested to know what happens. 我很想知道发生了什么事。（想了解）
I'm interested in working in Switzerland. Do you have any idea about that?
我对在瑞士工作感兴趣。你想过这事吗? （一种想法）
8.10 mean to doing/to do
mean to do 打算、想，mean doing 意味着。例如：
I mean to go, but my father would not allow me to. 我想去，但是我父亲不肯让我去。
To raise wage means increasing purchasing power. 增加工资意味着增加购买力。
8.11 begin（start） doing/to do
begin / start to do sth /begin / start doing sth.
1） 谈及一项长期活动或开始一种习惯时，使用doing。例如：
How old were