平时维持交感缩血管纤维紧张性活动的基本中枢位于（）
A.大脑
B.延髓
C.下丘脑
D.中枢和脑桥
E.脊髓中间外侧柱
参考答案：B
—Why are you so _____, Mei Mei?
—Because of the _____ news! I failed the test again! [ ]
A. frustrated, frustrated
B. frustrating, frustrating
C. frustrating, frustrated
D. frustrated, frustrating
需求量是指在某一价格下消费者愿意购买的某一货物的总数量。
