The very ubiquity of electronic communications can have a surprising downside , notes Richard Kohn, a military historian at the University of North Carolina: a wife becomes accustomed to frequent e-mail from her husband, until he can’’t get to a computer. And then her anxiety increases.

A．failure

B．underside

C．drawback

D．consequence

玻璃遮阳系数是通过窗玻璃的太阳辐射得热量与透过标准（）mm透明窗玻璃的太阳辐射得热量的比值。

A、2

B、3

C、4

D、5