瓷贴面修复的禁忌证中，错误的是（）
A.牙冠大部缺损牙
B.缺乏可粘结的釉质牙
C.前牙小间隙
D.反牙合或切牙合
E.重度夜磨牙
参考答案：C
种植某种树苗每棵成活的概率为p，若种植这种树苗5棵，则恰好成活4棵的概率为（ ）
A．C54p4（1-p）
B．C54p（1-p）4
C．p4
D．1-（1-p）5
I was out of town at thetime, so I don't know exactly how it ____. [ ]
A. was happening
B. happened
C. happens
D. has happened
