I shall paint the wall of my room green next Saturday if it doesn’t rain. It’s high time it ____.

It is (high) time that
选B.
It is (high) time (that)后面的从句谓语动词要用过去式,或用should加动词原形,但should不可省略.
It is time that the children went to bed.或者
It is high time that the children should go to bed.