My mom did all she could ______money for my education at that hard time.

题目

My mom did all she could ______money for my education at that hard time.
made
B：makes
C：to make
D：making
正确的答案应该是哪个?请高手赐教并给出详解

答案

C 表示目的,原句中she could 是做all的定语从句
在那段艰难的时候,妈妈做她能做的一切来赚钱给我读书.