A. pollution
Đáp án B
Health problem (n): vấn đề về sức khoẻ
Các đáp án còn lại:
A. pollution (n): ô nhiễm
C. (to) preserve (v): bảo quản
D. dirty (adj): bẩn
Ann's encouraging words gave me _________ to undertake the demanding task once again.
In the US the first stage of compulsory education _________ as elementary education.
The local people insisted that the road_________50 cm more so that, in case of flood, they still can travel on it.