灭菌
参考答案：杀灭物体所有上病原微生物（包括病原体、非病原体，繁殖体和芽胞）的方法，如高压蒸汽灭菌法。要求比消毒高。
___around Tiananmen Square, the tourists were taken to visit the Palace Museum. [ ]
A. Showing
B. Having shown
C. Being shown
D. Having been shown
过冷奥氏体高温转变（在Alr-...-550°C.的产物是（）体。
A.珠光
B.奥氏
C.铁素
D.渗碳
