哌唑嗪的降压作用是由于()
A.兴奋突触前膜α2受体
B.阻断突触后膜α1受体
C.兴奋突触前膜β2受体
D.阻断突触前膜β2受体
E.兴奋突触后膜α1受体
参考答案:B
—______ I come back before dinner?
—No, you ______. But you ______ be back later than 10: 30 p.m. [ ]
A. Need Amust; mustn 't
B. May; mustn't; can't
C. Can; can't; can't
D. Must; needn't; can't
等式I=I0e-μd中,表示入射射线强度的是()
A.I
B.I0
C.e
D.μ
E.d