两台服务器相距1千米，在传输大容量数据时，最适合的传输介质是（）。
A、屏蔽双绞线
B、非屏蔽双绞线
C、单模光纤
D、同轴电缆
参考答案：C
--- Look at ______ book on the desk . Is it ______ useful one ?
--Yes, it is . In the book there is much advice on how to learn math well.
A．a, the
B．the, a
C．the, an
D．a, an
不饱和脂肪酸（unsaturated fatty acid）
