?
A Electricity.
B Tungsten oxide.
C A battery.
D A voltage.
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,according to the last paragraph?
A The buildings will look different.
B Windows can be as large as you want.
C We may not need air conditioners any more.
D They are less expensive than traditional windows.
switch语句后括号里的表达式是什么类型?case后类型如何确定?
switch语句后,default关键字起什么作用?break起什么作用?