题目

As nobody here knows what is wrong with the machine, we must send for an engineer to ________ the problem. A. handle                               B. raise C. face                                 D. present 答案：A7．下列人类对微生物的利用中，合理的是（　　）A．用酵母菌制作米酒B．用大肠杆菌酿醋C．用乳酸菌制作酱油D．用细菌提取青霉素