短文填空。根据下列短文内容，根据首字母提示，在短文后的空格处填上一个恰当的词，使短文通顺，每空一词，含缩略词。

       Do you know the differences between the new building and the old ones?

       Old buildings h  1   brick(砖)and stone walls. The walls hold up the b  2  .

       In cities, many modern building 1  3   as if they are made just of windows.Walls of dark glass reach

high into the air.  Many buildings are m   4   than 50  stories(层)tall.

      Are walls of glass strong e  5   to hold up the new buildings? No, The new glass walls do not hold up

the buildings,b   6   they only cover up the frame(框架)made of steel.  Have you ever watched a new

building going up? The steel frame is built f   7  .  Then the glass walls are hung on the frame.  When the

building is f  8  , the frame does not show.  The outside looks like windows without walls. The glass walls

shine i  9   the sun with no decoration(装饰).Many people find t   10   beautiful just as they are.