by We must take steps to preserve natural resources; otherwise the planet will be in danger.
A. Unless we take steps to preserve natural resources, the planet will be in danger.
B. Unless we take steps to preserve natural resources,the planet will not be in danger.
C. If we take steps to preserve natural resources, the planet would be in danger.
D. If we take steps to preserve natural resources,the planet will be in danger.
Câu trả lời là: A là đáp án đúng
