An idea came to him ___ he might do the experiment in another way.

A．which

B．when

C．what

D．that

萌出间隙变小，邻牙缺隙处倾斜，恒牙不能正常萌出的原因是（）

A.乳牙滞留

B.牙齿迟萌

C.乳牙早萌

D.乳牙早失

E.融合牙