差动保护
参考答案：
是利用电气设备故障时电流变化而达到启动的保护。
斜疝与直疝最重要的鉴别标准是（）
A.疝块是否降入阴囊
B.患者年龄
C.疝块的外形
D.疝囊颈与腹壁下动脉的关系
E.疝块能否回纳
—Did you clean up the garden yesterday?
—Yes, I did. And my mother was _____ me. [ ]
A. pleased with
B. worried about
C. friendly to
