形成垂直食物嵌塞的最常见原因是（）。

A.颌面磨损均匀

B.邻牙边缘嵴高度不一致

C.龈 * * 退缩

D.食物溢出沟加深

E.颊、舌面龈退缩

An Intranet is (71) the application of Internet technology within an internal or closed user group．Internets are company (72) and do not have a (73) connection to the Internet．Used properly an Internet is highly effective corporate tool，capable of regularly (74) information to empower the workforce with the information needed to perform their roles．Used in this way，Internet represent a step towards the (75) office．

72（）

A．common

B．shared

C．special

D．specific