效度是指()
A.测器的稳定性
B.测器的可靠性
C.测器的准则
D.研究目的的准确度
E.以上都是
参考答案:D
龋病初期的临床特征中不包括()
A.牙釉质是白垩色
B.牙齿的透明度下降
C.牙体硬组织脱矿
D.牙釉质出现龋坏
E.腔卫生极差
There _____ a lot of coal mines in the south, but many of them have been closed or are _____ be closed.
A.use to having; about to
B.used to be; to
C.use to having; going to
D.used to be; supposed to