—Why are so many people gathering there?
—Several people seem ________.Let's go and see.
A:being dancing
B:dancing
C:to be dancing
D:to have danced
如图是人体在平静呼吸时肺内气体容量变化曲线,以下说法正确的是( )
①辩证的否定是事物联系和发展的环节
②创新推动了社会生产力的发展
③通过实践改变事物的属性,可以建立新的联系
④要素的优化组合有利于系统功能的充分发挥