Answer:
I transfer oxygen from the atmosphere to your blood
I open to close but I close to open. I'm surrounded by water but I'm never soaking. What am I?
What gets whiter the dirtier it gets?
The faster you run, the harder it is to catch me. What am I?
I am very easy to get into,but it is hard to get out of me. What am I?
I have a ring but no fingers. I used to stay still all the time but nowadays I follow you around.