大肠杆菌引起的食物中毒潜伏期为___小时，蜡样芽孢杆菌引起的食物中毒潜伏期为___小时。
参考答案：2～20；1～2
Somehow this seems to me to be _______. How could a team that had fought for Canada before suddenly become citizens of the USA?
A．out of question
B．out of place
C．out of shape
D．out of control
合成氨工业上采用循环操作的主要是因为
A．加快反应速率
B．能提高NH3的平衡浓度
C．降低NH3的沸点
D．提高N2和H2的利用率
