They said they would do what they could do （）（keep）the river from being polluted 动词填空
问题描述：
They said they would do what they could do （）（keep）the river from being polluted 动词填空
答
to keep 表目的
答
to keep
答
to keep.用不定时to do 表示目的
祝进步,不懂追问