一道选择题请说明理由

问题描述:

一道选择题请说明理由
Mum’s promised me that she ______ me a present for my 14th birthday.
A has given B had given C will give D would give
正确答案是C,D为什么不对

因为前面妈妈是has promise.
has可以看成是现在式吧
主句和后面的从句时态要一样,也就是都不需要用过去式
所以用will不用would