Answer:
A
They are Dark, and always on the run. without the sun, would be none!
What devours all and can kill a king. Destroy a town and crushes mountains down?
Handy when you need to measure something or run a kingdom.
What ship has no captain but two mates?
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.