坏疽性口炎的发病原因可能是（）
A.口腔卫生不良
B.维生素缺乏
C.局部创伤
D.病毒感染
E.细菌感染
参考答案：E
The president expressed his satisfaction with the co-operation, that he hoped to have another one.
A．adding
B．added
C．to add
D．having added
合作制律师事务所怎样理解？
