make it done or have it done

题目

make it done or have it done
-The head teacher is always saying my hair is too long.
-He's right.I think you'd better---it cut
A.have B.make c.to make D.to have
参考答案是B,谁能解释下,make/have/let是使役动词,有make sth done 的用法的

答案

A