有关牙的描述错误的是

A．分恒牙和乳牙

B．乳儿自6个月萌生乳牙，13岁左右全部出齐

C．切牙、尖牙为单根牙

D．牙颈外包以牙龈

E．牙分为牙冠、牙颈、牙根

It makes no________which road you take；both lead to the city,and they are equally long.[ ]

A．point  

B．sense

C．matter  

D．difference