题目内容：

Kate promised __ her little sister.A.her mother to look after B.to her mother looking after
C.to her mother to look after
D.her mother to looking after

优质解答

A,

追问：

能说下为什么吗

追答：

这是固定搭配啊，promise sb to do 一般除了make，let，have三个使役动词，其他及物动词都是加to do的