I’M SURE THE LETTER WON’T ARRIVE IN TIME UNLESS IT …(SEND)… BY AIR....

5. - KIỂM TRA TIẾNG ANH 15 PHÚT PPSX
Tiếng Anh KIỂM TRA TIẾNG ANH 15 PHÚT PPSX

5. I’m sure the letter won’t arrive in time unless it …(send)…

by air.

b- 1. saw / were singing / said / had been singing