Answer:
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.
I build up castles. I tear down mountains. I make some men blind. I help others to see.
I walked and walked and at last I got it. I didn't want it. So I stopped and looked for it. When I found it, I threw it away.
No matter how little or how much you use me, you change me every month.
What is it that given one, you’ll have either two or none?
What language does a billboard speak?
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?