OSI模型的哪一层描述了构成网络数据的物理信号？（）
A.7
B.4
C.1
D.3
参考答案：C
凡携带枪支饮酒的，一律予以开除。( )
Compared with his sister, Jerry is even more ______ to, and more easily troubled by, emotional and
relationship problems. [ ]
A. sceptical
B. addicted
C. available
D. sensitive
