单选题 The fire fighters sank down one by one, ______.
A. all their strength to exhaust B. all their strength exhausted
C. all their strength to be exhaust D. all their strength to be exhausted

【正确答案】 B
【答案解析】[考点] 独立结构。分词独立结构作伴随状语，通常置于句末，逻辑主语与该分词表示完成意义或被动意义，排除A，C，D。故选B。