题目

 _______his homework, he was not allowed to play out. A.Not finished              B. Having finished C. Having not finished        D. Not having finished 答案：D细菌和真菌可以引起人类的各种疾病，但有些真菌却可以产生杀死某些致病细菌的物质，如青霉能产生 ， 我们把这些物质称为 ．