红细胞比容多少时可维持理想脑血流量（）
A.40%～45%
B.35%～39%
C.30%～34%
D.25%～29%
E.20%～24%
参考答案：C
Huangshan is ________ most beautiful tourist site and I want to visit it ________ second time next month.[ ]
A. the; the
B. the; a
C. a; a
D. a; the
你认为西双版纳有哪些方面的旅游优势？
________________________________________________________________________________
