18. I didn't know the answer, so I couldn’t tell you. →If._________________________________________________ 19. I was able to come in time because Jane gave me a lift. →If._________________________________________________

`->`

18 . If I had known the answer , I could have told you

( Câu đk loại 3 , vế if là had + Pii , mệnh đề chính chia động từ khuyết thuyết ở dạng quá khứ + have + Pii+..)

19 . If Jane hadn't given me a lift , I wouldn't have been able to come in time

( Câu đk loại 3 )

$#Minh$