1) He might have forgotten to check in.

他可能忘了报到
2) He has most likely forgotten.

他很可能忘了。
3) but he was feeling tired,

可他感到累了,
4) Mind you don't forget it.; Be sure to remember it.

可别忘了。
5) He may have gone.

他可能走了。
6) He neglected to return the book.

他忘了还书。
参考词条