一个圆锥体的底面半径扩大2倍，高缩小为原来的一半后，它的体积与原来的体积相比[ ]
A．缩小2倍
B．没变
C．扩大2倍
D．扩大了4倍
答案：C
_____ three times in a row, the boxer decided to give up fighting. [ ]
A. Having defeated
B. To have defeated
C. Having been defeated
D. To have been defeated
水中酚易被微生物分解和氧化，因此采样时必须在现场加保存剂固定，并在一定条件下保存，常用的方法是（）
A.A
B.B
C.C
D.D
E.E
