正常的脐带结构是（）。
A.一条动脉，一条静脉
B.一条动脉，两条静脉
C.两条动脉，一条静脉
D.静脉较粗壁厚
E.动脉较细壁薄
参考答案：C
At present, blogs are ______ traditional diaries (日记) among young people.[ ]
A. very popular
B. as popular as
C. not so popular as
D. much more popular than
以下指标中属于空头市场的是( )。
A．DIF和DEA为正值
B．DIF和DEA为负值
C．短期RSI小于长期RSI
D．短期RSI大于长期PSI
