2. Grammar: infinitives are common non-predicate verbs in English. Although it can't act as a predicate verb, it can act as almost all sentence components except the predicate, such as subject, predicate, object, adverbial, attribute, complement and so on. Generally speaking, infinitives are composed of "to+ verb prototype". But in special cases, the infinitive marker to is often omitted. These special cases of omitting to are as follows: ① Coming and going in spoken language follow. ② Compare the structure behind than. ③ Behind causative verbs and sensory verbs. ④ After the verb help.
3. Example: Omit the verb inequality of to
Go and get some water. Go and get some water.
I'd rather stay here than go at once. I'd rather stay here than leave at once.
I saw some old people dancing in the square. I saw some old people dancing in the square dance.
Planting trees helps to make our city cleaner and more beautiful. Planting trees can help cities become cleaner and more beautiful.