脑栓塞栓子主要来源于
A．心脏
B．肺静脉
C．下肢静脉
D．败血症
E．脂肪
参考答案：A
------They are said to be quarrelling about our new language lab.
------ I don’t care. It has __________ to do with me.
A．nothing
B．something
C．anything
D．everything
低压断路器触点的磨损超过厚度的1/3以上或超程减少到（）时，就应更换新触点。
A、1/5
B、1/4
C、1/6
D、1/2
