it kept-----for three days,A on raining B to rain C rained D rain 怎样选择?

问题描述:

it kept-----for three days,
A on raining B to rain C rained D rain
怎样选择?

A keep on doing sth 持续/继续做某事

A
keep on doing sth 持续不断地做.
这里只已经连续下了3天雨了