口腔前庭内，位于中线上的解剖标志为（）
A.切牙乳突
B.舌系带
C.上颊系带
D.下颊系带
E.唇系带
参考答案：E
Which of the following statements regarding a forward commitment is FALSE A forward commitment :()
A. is a contractual promise.
B. involves an action in the future.
C. is not legally binding and can involve a stock index.
什么是异质结？按照两种材料的导电类型不同，异质结可分为哪些类型？异质结形成的条件是什么？制造异质结的技术通常有哪些？
