-Why are they pulling down the house?

题目

-Why are they pulling down the house?
-( ) a new parking lot.
1.Build
2.To build
3.Building
4.Built
很多题都是类似的这四种选项.
它们之间到底有什么区别?

答案

Build ...是祈使句;
To build ...是不定式作目的状语,前面省略了They pulling down the house to build a parking lot;
Building ...可以作伴随状语,表示伴随的动作,但在这里不符合语境；
Built ...这里说不通.