在我国，该漫画所揭示的问题表现比较严重的地区是
A．华北地区
B．沿海地区
C．西北地区
D．东北地区
答案：C
Chinese students usually spend ______ the students of the US studying in their free time.
A．twice as many hours as
B．as twice many hours as
C．twice hours as many as
D．as many as twice hours
就造血多能干细胞而言，下述说法正确的是
A．仅存在于骨髓中，其形态和淋巴细胞相似
B．在特定条件下，可在脾内形成造血结节
C．大多数细胞表达CD38和Thy-1
D．不能产生淋巴细胞干细胞
E．其增殖形式为对称性增殖
