采集血液，需要抗凝剂，血站通常保存血液用的抗凝剂为（）。
A.肝素
B.二乙胺四乙酸二钠
C.华法林
D.枸橼酸钠
E.葡萄糖酸钙
参考答案：D
The photo was taken ______ stood the famous Bird’s Nest in Beijing during the Olympics.
A．which
B．in which
C．where
D．there
光纤通信的光波波长在（）之间。
A.0.8μm～1.8μm
B.1.8μm～2.8μm
C.2.8μm～3.8μm
D.3.8μm～4.8μm
