Answer:
What stays the same size no matter how much they weight?
I cost no money to use, or conscious effort to take part of. And as far as you can see, there is nothing to me. But without me, you are dead.
I am the red tongue of the earth, that buries cities.
There are several different kinds, but the one you pick doesn't do its job. What is it?
What's a place you have left but didn't enter?
I always murmur but never talk. Always run but never walk. I have a bed but never sleep, have a mouth but never speak. What am I?