A：背斜
B：向斜
C：断层
D：褶皱
—________.
She was so busy ____(look) for her mobile phone that she didn't see a car coming.
下列各句中，划线的成语使用恰当的一项是( )
太阳光球层和色球层分别出现的太阳活动主要标志是( )
