在高温下易破坏的毒素是（）
A.黄曲霉毒素
B.河豚毒素
C.蜡样芽孢杆菌产生的呕吐毒素
D.肉毒毒素
E.葡萄球菌肠毒素
参考答案：D
Why did the share prices get a shock yesterday().
A.Because the pound fell to its lowest level against the dollar.
B.Because the American currency soared to a new peak.
C.Because the Footsie slumped forty-two points.
D.Because the government increased interest rates to fifteen per cent.
使用二氧化碳对电气设备进行灭火时要注意安全，当空气中二氧化碳浓度达到（）时，会使人窒息。
A、50%
B、30%
C、10%
D、20%
