Those stones,each weighing as much as four tons,came from the Alps Mountains.
问题描述：
Those stones,each weighing as much as four tons,came from the Alps Mountains.
现在分词weighing在句中什么作用?定语?这是一道选择题,为什么不选动词不定式to weigh
答
each weighing as much as four tons 这是独立主格结构.一般来说,动词不定式用于表示目的和即将发生的事情,这里显然不是.