1. 過去進(jìn)行時(shí)

• 用于談?wù)撨^去某個(gè)時(shí)間正在發(fā)生的事情I was playing football at 3:30 yesterday.

• 用于談?wù)撛谶^去某個(gè)時(shí)間同時(shí)發(fā)生的兩件事He was doing homework while his sister was watching TV.

• 過去進(jìn)行時(shí)與一般過去時(shí)在同一個(gè)句子里出現(xiàn)的情況：I was doing homework when my sister came to talk to me.Someone knocked at the door while my mother was cooking.

• 否定句、疑問句的表達(dá)方式:He was not/wasn't working.They were not/weren't speaking to each other.Was he working? Yes, he was/No, he wasn't.Were they speaking to each other? Yes, they were/No, they weren't.

2. can/can't/could/couldn't

• 在有些時(shí)候，could可以作為can的過去式使用

• can/can't表示能力，用于現(xiàn)在時(shí)I can help you.（我能幫助你）

• could/couldn't表示能力，用于過去時(shí)，。比較：I couldn't come yesterday.（我昨天不能來）I could have come yesterday.（我昨天能來，但是沒來）

• can/can't表示可能性，用于現(xiàn)在時(shí)This can't be true.（這不可能是真的）

• could表示可能性，用于過去時(shí)，或者用于現(xiàn)在時(shí)但語氣沒有can強(qiáng)烈He couldn't go there without me.（他不可能不帶我一起去）

• can/could還可以在現(xiàn)在時(shí)中用于請(qǐng)求，區(qū)別在于could比can語氣更委婉客氣Can you help me please?Could you please open the door?

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