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"。

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，而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。

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。

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)

mean to doing/to do

mean to do　 打算、想

mean doing　意味着

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. 赠加工资意味着增加购买力。

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.

How old were you when you first started playing the piano? 你几岁时开始弹钢琴？

2) begin, start用进行时时，后面动词用不定式to do

I was beginning to get angry.　我开始生起气来。

3) 在attempt, intend, begin, start 后接know, understand, realize这类动词时，常用不定式to do。

I begin to understand the truth.　我开始明白真相。

4) 物作主语时

It began to melt.

感官动词 + doing/to do

感官动词 see, watch, observe, notice, look at, hear, listen to, smell, taste, feel + do　 表示动作的完整性，真实性；+doing 表示动作的连续性，进行性

I saw him work in the garden yesterday.　昨天我看见他在花园里干活了。(强调"我看见了"这个事实)

I saw him working in the garden yesterday. (强调"我见他正干活"这个动作)昨天我见他正在花园里干活。

典型例题

1) They knew her very well. They had seen her ___ up from childhood.　

A. grow　 B. grew　 C. was growing　 D. to grow

答案：A. 因题意为，他们看着她长大，因此强调的是成长的过程，而非正在长的动作，因此用see sb do sth 的句型。

2) The missing boy was last seen ___ near the river.　

A. playing　 B. to be playing　　C. play　　D. to play

答案：A. 本题强调其动作，正在河边玩，应此用see sb. doing sth句型。