Nobody taught _____ Chinese. He learned all by ______. What a clever boy!

A．himself; him

B．him; himself

C．his; himself

D．his; him

下述上颌第二前磨牙与上领第一前磨牙形态区别中错误的是

A．上颌第二前磨牙的颊尖比较圆钝

B．上颌第二前磨牙在近中面无近中沟

C．上颌第二前磨牙牙颈外形略宽

D．上颌第二前磨牙多为扁形双根

E．上颌第二前磨牙邻面更圆凸