此心电图诊断为（）
A.室性期前收缩
B.房性期前收缩
C.变界性期前收缩
D.室性心律
E.正常心电图
参考答案：A
An inflatable liferaft should be manually released from its cradle by（）.
A.cutting the straps that enclose the container
B.removing the rubber sealing strip from the container
C.loosening the turnbuckle on the securing strap
D.pushing the button on the hydrostatic release
合金元素的加入使钢的淬透性得到显著（）
A.提高
B.降低
C.变化
