单项选择题经过灭菌处理而未被污染区域为:A. 有菌区 B. 无菌区 C. 半污染区 D. 清洁区
单项选择题What are mutually exclusive investment projects? If two investment projects are mutually exclusive, that is to say, if we accept one of them, we can't accept another project. A、正确 B、错误