The non-finite verbs are so called because they are not marked for tense or for subject-verb concord.This week we mainly talked about infinitive.There are two types of infinitive:to-infinitive and bare infinitive.Infinitives commonly occur wiht to,but in some contexts it it necessary to use the bare infinitive,and in some other cases the infinitive sign is optional.So we must figure out in what situations we should use to or bare infinitive.Some verbs can be directly followed by an infinitive to form a verb-object relation.And these collocations fall into three types:
1,verb+infinitive
2,verb+object+infinitive
3,verb+(object)+infinitive
and there are also some points we must pay attention to.

课后练习

Why don't you get your wife____explain it to you?

答案：to

解析：why.../why not...句式中，紧接why之后的不定式总是不带to.而题目所要求填并不是紧跟why的不定式，因此to不能省。

Help the girl in front of you_____carry the baskets.

答案：to

解析：help之后即可用不带to不定式也可用带to不定式。

Don't forget to have him____come.

答案：/

解析：let, make , have等使役动词+宾语之后用不带to不定式。

The children are making____believe that they're princes and princesses.

答案：to

解析：使役动词为被动态时，不带to的不定式转为带to不定式

What he did was_____throw his arms around the boy and embrace him.

答案：（to）

解析：SVC句型中如果主句部分有动词do的某种形式，则作主语不予的不定式即可带to也可不带to.

I'd sooner____die than____marry him.

答案：/, /

解析：would rather/would sooner/would (just) as soon, may/might (just) as well, cannot but/cannot help but等情态成语之后跟不带to不定式。前三个之后也能跟than-/as-分句，在这种分句中用不带to不定式。

It's not a serious error; we can_____.

答案：let it pass

释义：let (it, etc) pass 不予理会

And as for Joe and Betty Turner, well, they're not the neighbors I'd have chosen and never will be, but we _______.

答案：live and le t live

释义：互不相扰

At a very early stage, Paderewski revealed that he was a master of the keyboard.

答案：himself to be

The police believed their informant to be reliable.

答案：that their informant was reliable