Câu 3: Erosion, which washes away valuable topsoil, can prevent by planting trees and grass.
A. washes B. can prevent C. by D. grass
Câu 4: That pottery was found by an archaeologist while she was worked in this area.
A. was B. found C. by D. was worked
Câu 5: The children are only allowed watching television on the weekend.
A. The children B. only C. watching D. on
Câu 6: You can't go into the reception if you've got a ticket.
A. can't B. into C. if D. 've got