The doctor told Penny that too much ____to the sun is bad for the skin.

　　A. exposure B. extension C. exhibition D. expansion

　　[exposure]

　　exposure 暴露

　　[/exposure]

　　[extension]

　　extension 伸展，扩展

　　[/extension]

　　[exhibition]

　　exhibition 展览

　　[/exhibition]

　　[expansion]

　　expansion 膨胀