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。
We should balance our work and relaxation, and only by doing that, as everybody would agree,
____ a good state of mind. [ ]
A. can we have
B. we do have
C. we will have
D. we must have
灯光开关在该位置时，后雾灯点亮。
