患者,女,28岁。结婚3年,夫妇同居未孕,月经先后不定期,量少,色黯,经前 * * 胀痛,舌淡红苔薄白,脉弦。其证候是
A.肾虚
B.脾虚
C.肝郁
D.血虚
E.血瘀
参考答案:C
It is _______ unusual thing for us to find ________ UFO.
A.a; a
B.an; an
C.a; an
D.an; a
换热器的冷热流体采用顺流布置与逆流布置时各有什么优缺点?