be動詞有以下幾種主要形式：am,is, are, was, were,其中am, is, are表示的是現在，was, were 表示的是過去，所以be+動詞ing形式可以表示兩種時態：第一種，現在進行時(am/is/are+動詞ing形式)，比如說，We are having class now. 第二種，過去進行時(was/were+動詞ing形式)，比如 Li Ming was doing his homework

at eight o'clock yesterday evening.

be的ing形式: being
Thebeingof people is complex, and there is no way to generalize.

人的本性是複雜的，沒辦法一概而論。

This war has claimed thousands of livingbeings.

這場戰爭奪走了成千上萬生命。

Ourbeingshould not be based on the destruction of nature.

我們的存在不應以破壞大自然為前提。

Humanbeingshave various emotions and feelings.

人類有各種情緒和感覺

When you slack off, it affects me. Stopbeingso lazy!

你偷懶的時候會影響到我。所以不要這麼懶！

They are notoriously known forbeingbad customers.

他們是名聲狼藉的客戶。