稳压二极管正常工作时，其状态处于（）.
A、截止状态
B、击穿状态
C、饱和状态
D、振荡状态
参考答案：B
We can't decide ________.[ ]
A. to buy which book
B. which to buy the book
C. buying which book
D. which book to buy
乳腺恶性肿瘤的钙化特点为（）
A.钙化灶比较分散
B.钙化的密度比较一致
C.钙化多较粗大
D.钙化多呈细小砂粒状
E.钙化的边界清楚
