3/When did you hear from Robert ?
-> How long is it been since you last heard from Robert? (đã bao lâu kể từ lần cuối bạn nghe tin từ Robert)
4/It isn’t necessary for students to wear uniforms today.
->Students needn't wear uniforms today. (Hs k cần mặc đồng phục hnay)
Xin ctlhn