题目

The human body is designed to move. But modern lifestyles and office jobs rarely give us the chance to move around. As we know. we're while we're eating; we sit in the car and we sit while we watch TV. And many of us sit for many hours at work. New research shows that sitting less than three hours a day might extend your life by two years. Peter Katzmarzyk, a scientist at the University of Louisiana in the southern United States, says that sitting is ubiquitous in our lives, meaning it is something we do all the time, everywhere. However, Mr. Katzmarzyk says that does not mean you can s肺是呼吸系统的主要器官，是由许多肺泡组成的，下列有关肺泡的叙述中，与气体交换无直接关系的是（ ）A．肺泡数目极多B．肺泡位于细支气管的末端C．肺泡外包绕着毛细血管D．肺泡壁只由一层上皮细胞构成