所谓的逗号,不是用于省略连接词的并列句,就是诸如存在同位语的情况。英语也是CC党哈[ Clear and Concise ]。就给你还原一下哈:
It rained for a week. It's ruining our holiday.
He was considered the best player in the world in those days while he moved a basketball skillfully...
现在,你觉得这两个词的时态或形式好理解了吗?正因为是同主语,所以省略得较多。