光从一种介质斜射入另种介质，传播方向______偏折，这种现象叫做光的折射．光从一种介质垂直射入另一种介质，传播方向______偏折．光从空气斜射入水中或其它介质时，折射光线______法线方向偏折，光从其它介质斜射入空气时，折射光线______法线方向偏折．

How is the quartz heater different from other types of heaters
A. It heats only the objects in a room.
B. It is lighter in weight.
C. It heats the room quicker.
D. It is more common.