感染创面植皮前准备工作应做到

A．控制创面上的乙型溶血性链球菌

B．根据细菌培养和药敏试验，选用合适的抗生素，加强营养支持

C．以上都是

D．创面湿敷或浸泡，充分引流

E．必要时用手术方法清除失活组织

There are fewer teaching positions left in big cities, ____ at the same time there are shortages of teachers in

small towns. [ ]

A. or

B. and

C. so

D. for