酵（臭）米面食物中毒的病原物质为（）。
A.肠毒素
B.米酵菌酸
C.内毒素
D.组胺类物质
E.外毒素
参考答案：B
When I met him the other day, it was the first time we ____ each other since we were at school. [ ]
A. saw
B. had seen
C. were seeing
D. have seen
用树状结构表示实体之间联系的模型是
A．关系模型
B．网状模型
C．层次模型
D．以上3个都是
