Edit *like
Yes. Underwater caves do exist. Many formed when sea levels were lower than they are now and were flooded when sea levels rose.
well, you don't breath carbon dioxide, you breath oxygen
There are 8 worlds and 32 levels. There are 11 bonus areas (underground, underwater, &clouds).
NO! He's a character that you sometimes find in different levels of the adventure games, unless you're talking about something that mario gets powers from.
Sometimes it might be the case. Sometimes it is not that case also. It sometimes increases the stress levels sometimes makes that person stress free.
Why would you become short of breath at high altitudes if air at those levels still contains 21% oxygen
you can't download levels you can however download characters which can change levels depending on the character...
you just press nina as the character, then you can play with her or sometimes you have to beat so many levels it all depends on what kind of web site you are on.
It makes it hard to breath and, if severe, lowers oxygen levels.
Levels can not be granted Cross Faction. So, no, you can not give your alliance character points from your horde character.
normal people take breaths because of a decrease in their pH. if you hold your breath your co2 levels increase and that triggers your pH to go down, which makes you take a breath.
You can be unconcious and have a SaO2 of 100%.... but say your having difficultys breathing, if your O2 level drops below 94% Oxygen is needed, about 15% on a Nasal Canula. But if your passing out due to lack of O2, then it would have to be down around 85-90% but mind you.. that's not good. Plus, you cannot hold your breath and bring your O2 levels down. You will on the otherhand pass out if you hold your breath too long, not because your O2 levels are low, but because your body takes over so it can make itself breath again. Sometimes, your body can outsmart you.