the forest fire would have been discovered much earlier.A. But for their careB. Had they

问题补充：

, the forest fire would have been discovered much earlier.

A. But for their care

B. Had they been more careful

C. Without their care

D. If they were careful

答案：

A. But for their care

(答案→)B. Had they been more careful

C. Without their care

D. If they were careful

解析：考查特殊句式。A.要不是他们的关心 B.如果他们更谨慎点

C.没有他们的关心 D.如果他们很小心。

结合下文，森林大火会被更早的发现。可知选B最符合语境。