Susan was expecting her favourite singers,but to her disappointment,         appeared  .  [ ]

A. some          

B. none            

C. everyone      

D. no one    

如图所示为一沾有肥皂膜的闭合金属框，若将膜面上棉线圈内部的膜戳破，棉线会被拉成圆形，这是因为________的作用；与戳破前相比，肥皂膜的内能________(选填“增加”、“减少”或“不变”)。