已婚妇女，盆腔CT扫描为了显示 * * 和宫颈的部位，应放置（）
A.避孕环
B.碘油
C.纱布塞子或 * * 栓
D.硫酸钡
E.碘水
参考答案：C
_______ they worked very hard, _______ they didn't finish their work. [ ]
A. Although; but
B. Though; but
C. /; and
D. Although; /
评价指标的概率分布可采用( )方法。
A．分布估计
B．数理统计
C．历史统计
D．模拟计算
E．理论计算
