Being able to speak another language fluently is a great________when you're looking for a job.[ ]

A．chance  

B．success

C．effort  

D．advantage

恒牙迟萌的原因中与遗传性因素有关的因素是（）

A.牙根弯曲阻生埋伏

B.多生牙、牙瘤、囊肿

C.乳牙滞留

D.颅骨锁骨发育不全

E.先天性甲状腺分泌缺乏