After he _______ in a factory he opened a small business.
A. has worked
B. had worked
C. would work
D. was working
Đáp án B
I think we should have our house painting because it looks too dirty.
The situation is serious. Something must ___________ before it’s too late.
Species that have already lost habitat because of deforestation were given higher priority in the plan because of their greater risk of extinction.
The Red List has been introduced to raise people’s _______ of conservation needs.