把钠放入滴有石蕊试液的水中，下列现象不易观察到的是（ ）
A．钠浮在水面上
B．溶液中产生较多气泡
C．水溶液变为蓝色
D．钠熔化成小球并在水面游动
答案：B
女，25岁，咳嗽、咳痰、活动后气急1个月余，查体发现右下肺局限性干鸣音，已拍胸片，x光片尚未拿到
该患者首先需要排除的疾病是（）.
A.支气管内膜结核
B.支气管肺癌
C.渗出性胸膜炎
D.支气管扩张
E.慢性支气管炎
There are so many kinds of CDs in the shop. We can't decide ______. [ ]
A. what to buy
B. to buy what
C. which to buy
D. to buy which
