下列能引起咯血的原因是（）
A.支气管扩张
B.风心病二尖瓣狭窄
C.流行性出血热
D.门静脉高压
E.系统性红斑狼疮
参考答案：A, B, C, E
用7812等元器件制成串联调整稳压电源，则7812输入的电压大约为（）伏，变压器次级的交流电压大约为（）伏。
The force resulting from the earth’s rotation that causes winds to deflect to the right in the Northern Hemisphere and to the left in the Southern Hemisphere is called（）.
A.Pressure gradient
B.Coriolis effect
C.Aurora borealis
D.Ballistic deflection
