流星发光是因为()
A.反射阳光
B.自身发光
C. 摩擦碰撞
D.月光反射
参考答案:C
解析:摩擦生热。流星下落速度很快,与地球大气摩擦,温度极高,便会发光。
赤道是:( )
A.30º纬线
B.90 º纬线
C.0 º纬线
D.20 º纬线
He had no idea how much a room in this hotel______.
A.was charged
B.charged
C.was charged for
D.charged for