热转移设备的升温步骤是先开启主电源，然后松开AB工位急停开关，然后按绿色启动键，最后开启两工位加热开关。
参考答案：对
- Has your friend completed his design? - Not yet. He ________ on it last night.
A．worked
B．has worked
C．is working
D．was working
蛲虫虫卵从接触空气到成为感染性虫卵的时间为（）
A.2小时
B.3小时
C.4小时
D.5小时
E.6小时
