对无牙颌病人,若上、下颌骨关系正常,则上、下牙槽嵴的连线与平面的交角()
A.大于60°
B.小于60°
C.大于80°
D.小于80°
E.等于70°
参考答案:C
He _____________ a trip to Beijing.
A. have
B. does
C. do
D. has
若aAn+与bB2-两种离子的核外电子层结构相同,则a的数值为( )
A.b+n+2
B.b+n-2
C.b-n-2
D.b-n+2