but when they cross a busy road_using__a crosswalk,traffic is held up.为什么用using.求详细解释!
问题描述：
but when they cross a busy road_using__a crosswalk,traffic is held up.为什么用using.求详细解释!
答
when they cross a busy road 这个分句当中已经有谓语了 如果再加一个动词进去 那就要用非谓语的形式 有三种 ing p.p to do 即现在分词,过去分词 ,和不定式 其中现在分词表主动,过去分词表被动 ,不定式表目的.use a crosswalk 明显是they 发出的动作 且伴随着they cross a busy road 发生 所以要用using !