牛津实用英语语法:312 could用于间接引语

　　A could表示能力

　　1 could表示目前的能力时在间接引语中保持不变：

　　I cant/couldnt stand on my head，he said.

　　他说：我不能做三点倒立。相当于：

　　He said he couldnt stand on his head.

　　他说他不能做三点倒立。

　　2 could表示将来的能力时，在间接引语中可以保持不变，或由would be able结构来转述：

　　He said，I could do it tomorrow.

　　他说：我明天能做这事。相当于：

　　He said he could do it/would be able to do it the next day.

　　他说他第二天能做这事。

　　3 条件句类型2中，主句中的could与A2中的变化相同：

　　If I had the tools I could mend it，he said.

　　他说：如果我有工具的话，我就能修补它。相当于：

　　He said that if he had the tools he could/would be able to mend it.

　　他说如果他有工具的话，他就能修补它。

　　would be able在这里暗指所假设的情况有可能实现(可能他可以借到工具。)

　　4 条件句类型3中，could被转述时保持不变。

　　5 could表示过去的能力时，在间接引语里保持不变，或用had been able结构转述：

　　I could read when I was three!she boasted.

　　她吹嘘说：我三岁时就能看书了!相当于：

　　She boasted that she could/had been able to read when she was three.

　　她吹嘘说她三岁时就能看书了。

　　B could表示允许

　　1 条件句类型2中的could在间接引语中可保持不变，或由would be allowed to转述：

　　If I paid my fine I could walk out of prison today，he said.

　　他说：如果我交了罚款，我今天就能走出牢门了。相当于：

　　He said that if he paid his fine he could/would be allowed to walk

　　他说如果他交了罚款他会被允许走

　　2 表示过去时态的could在间接引语中可保持不变，或用 was/were allowed to或had been allowed to结构来转述：

　　He said，When I was a boy I could stay up as long as I liked.

　　他说：我小时候，我可以想呆到多晚睡觉就呆到多晚。相当于：

　　He said that when he was a boy he could/was allowed to stay up./He said that as a boy he was/had been allowed etc.

　　他说他小时候，可以/被允许爱呆到多晚睡觉就呆到多晚。