The camcorder's iris opens and closes just like the iris in the human eye.摄录机的虹彩光圈就像人眼的虹膜一样开合。A 20,000-seat arena with a retractable roof is planned.一个有两万个座位、带可开合顶棚的体育场正在规划中。The curtains are for purely decorative purposes and do not open or close.这些窗帘纯粹用来装饰，不能开合。