1 Neil Armstrong was the first person to set foot on the surface of the moon.( thiếu đề )
-> chỉ vật duy nhất là mặt trăng -> dùng the
2 At the end of the race, he was exhausted and collapsed on the ground.
-> on the ground
3 Have you finished doing the homework the teacher gave us last week?
-> finish + Ving
4 If I had money now, I would buy a cellphone.
-> If 2 : If + S1 + V2/ed, S2 + would + Vinf