单选题 Sam did nothing else than ______ when he saw the old lady fell down on the ground.

【正确答案】 A

【答案解析】[精解] 固定搭配题。"do nothing else than do something"结构，意思为只做什么，than后面的动词不定式通常不带to，如：He could do nothing else but wait．他只能等。因此答案为[A]。