Is it John that is being scolded in the manager’s office?

No. It ______ be him. I saw him on the way just now.

A．mustn’t

B．won’t

C．can’t

D．may not

关于氟牙症的描述不正确的是

A．受害区柱间发育不全或完全消失

B．透射电镜下观察与正常釉质不同

C．氟牙症者少发生龋

D．光镜观察釉基质有缺陷

E．严重者釉质有缺损且有色素沉着