I like this house with a garden in front,but I don't have enough money to buy____.A.that B.it C.this D.one 答案是A.为什么?A和B有什么区别?

I like this house with a garden in front,but I don't have enough money to buy____.
A.that B.it C.this D.one 答案是A.为什么?A和B有什么区别?

这个句子的前半句提到this house,因此在后半句用that来对应
如果前半句用a house,后半句就可以用it来指代

答案应该是B