库血保存时间不超过（）
A.3天
B.1周
C.3周
D.4周
E.5周
参考答案：C
解析：目前常用抗凝剂CPD和ACD抗凝血可保存21天。
A security market with price continuity is most accurately characterized as a market in which:（）
A. assets can be bought or sold quickly.
B. an asset’s price reflects all available information about the asset.
C. prices do not change much from one transaction to the next in the absence of new information.
下列有关区域的说法正确的是
A．区域划分的指标和方法是固定的
B．区域之间有明确的边界
C．区域是最小的单位不可分割
D．每一个区域都具有特定的地理环境条件
