Perfect infinitive means the action happed before the main verb.

完成不定式表示动作发生于主要动词之前.

Adverbs of frequency are placed after the verb 'to be' when used as the main verb of the sentence.

当be动词作为一个句子的主要动词时，频率副词位于be动词之后。

We have the subject, an auxiliary verb, the negative not, and our main verb.

我们有主语，助动词，否定词not，还有主动词。

So we have our subject, and auxiliary verb, and our main verb in our statement.

我们的陈述句中有主语、助动词、助动词。

You normally put adverbials of manner, place, and time after the main verb.

方式状语, 地点状语和时间状语通常都置于主动词之后.

The choice of a non-finite verb form after the main verb in an English clause has been one of the trickiest problems in English grammar.

英语小句中非限定动词的选择问题一直是困扰中外学者的难点之一。

You usually put adverbials of frequency, probability, and duration in front of the main verb.

表示频率, 可能性和持续性的状语一般放在主动词之前.