1 表示能力两种时态can (could),其他时态要用be able to的形式 He can speak French. Was/were able to 可以表示成功做成某事的含义* managed to do / succeeded in doing With our help, he was able to build the house. 2 表示请求或许可 Could 比 Can 更加客气* may Can I go now? Yes, you can.
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