液化石油气的爆炸极限是（）。
A.2－10%
B.5－15%
C.5－25%
D.10－20%
参考答案：A
戏剧《牡丹亭》的作者是[ ]
A．关汉卿
B．马致远
C．孔尚任
D．汤显祖
It was along the Mississippi River ________ Mark Twain spent much of his childhood.[ ]
A. how
B. which
C. that
D. where
