1.It is in the mall _ her purse had been sliced open _she was robbed of her necklace.
A that,where B where ,that
（答案是B,我知道一个是强调句,一个是定语从句,但为什么一定是前一个是定从,后个是强调句?为什么不能选A）
2.Mary _ all the housework ,she dropped herself into the sofa.
A having finished B finishing
(答案是A,为什么不能选B,