we need to protect animals中to protect做什么语

to protect为动词不定式作宾语
不定式作宾语有两种：一种是及物动词后直接跟带to的不定式；另一种是"动词＋疑问词＋带to的不定式"

(一)动词＋带to的不定式结构
只能跟动词不定式的动词,常见的有：afford, agree, aim, appear, arrange, ask, believe, care, claim, decide, decline(拒绝), demand, desire, determine, endeavor, expect, fail, hesitate, hope, intend, learn, long, manage, mean(想要), offer(表示愿意做...), pretend, promise, refuse, seek(试图), swear, undertake, wish(想要)等.
(二) 动词＋疑问代(副)词＋不定式
这类动词常见的有：advise,decide, discuss, find out, forget, inquire, know, learn, regard, remember, see, settle, teach, tell, think(=consider), understand, wonder等.这些疑问代(副)词有what, when, where, which, how, whether等,但不包括why,
(三)有时,不定式跟作主语时一样,可由it来代替,而把不定式放到后面去
He makes it a rule to take a walk before breakfast.
I think it interesting to play football while it is snowing hard.
We find it difficult to get everything ready before the time you require.
She cosiders it important to make friends with them.
I don't think it necessary to argue with them on this problem.
(四)有时THERE和TO BE连用表示"有"或"存在(某情况)"等
It is impossible for there to be any more.
Would you like there to be a meeting to discuss the problem?
I expect there to be no argument about this?
有时在个别的介词后可用"疑问词＋不定式结构"作其宾语
He has his own decision of how to do it.