they are having a great time___in the pool.横线上是填to swimming 还是swimming 为什么?急用.
问题描述：
they are having a great time___in the pool.横线上是填to swimming 还是swimming 为什么?急用.
答
swimming,to是不定式后面要跟动词原形,这里的swimming是现在分词做状语.