couldn't 同义句为什么要变过去式

来源：学生作业帮编辑：作业帮分类：英语作业时间：2024/05/15 08:48:48

couldn't 同义句为什么要变过去式
用适当的动词和情态动词填空 They couldn't find any secrets.=They ( )not( )to find any secrets.
was able
问：1.为什么不是were,able
2.能否是are ,able？抑或因为could 是can 的过去式，所以词形转换必须过去时？

could不光是Can的过去式,单独使用表示用于假设语气的条件句
再问：用适当的动词和情态动词填空 They couldn't find any secrets. =They ( )not( )to find any secrets. 答案：was ，able 问：1.为什么不是were,able 2.能否是are ,able？抑或因为could 是can 的过去式，所以词形转换必须过去时？
再答： 1,应该用were , able, they是复数，用was怎么看也不对 2，不能用are，able，就是因为是用了过去式

couldn't 同义句为什么要变过去式 We couldn't find them all.变同义句We couldn't find_____of_____. The water was so dirty that we couldn`t drink.变同义句怎么变呀 It couldn’t be better 为什么用过去式 couldn't是过去式吗 The birds couldn't fly in the shy.同义句 I couldn't go forward.的同义句是什么,谢谢. He couldn't come back today（改同义句）改为同义句Somethings he couldn't make complete sentences I couldn't find my pen anywhere的同义句 He couldn't finish the work yesterday 同义句转换 He couldn't answer the question correctly 改为同义句