她小时候能背诵整本诗集。

She ___could recite entire poetry books when she was little.

你能帮我拿一下那个包吗？

___Could you help me with that bag?

我可能把钥匙落在办公室了。

I ___could have left the keys in the office.

如果你早点起床，就能赶上第一班火车。

If you wake up early, you ___could catch the first train.