I ____________ a storybook that night.[ ]
A. buy
B. bought
C. to buy
D. buys
答案:B
石油埋藏在地底下,一般在地表不能看到,勘探工作者首先从()入手找油。
计算2x2•(-3x3)的结果是( )
A.-6x5
B.6x5
C.-2x6
D.2x6