瓦斯是完成突出过程的主要因素，是抛出煤体并进一步破碎煤体的主要动力。
参考答案：对
Did you spend 20 dollars ________ this computer game? [ ]
A. to buy
B. pay
C. buying
D. paying
— Is there a TV in your bed room?
— _______. But there is a big TV in the living room. [ ]
A. Yes, there is
B. Yes, it is
C. No, there isn't
D. No, it isn't
