Good Riddles

Question: Surrounded by life , yet life is its biggest enemy. But without life there is no need for it to exist. What is it?

Question: Something all men have,
but all men deny.
Man created it,
but no man can hold it.

What is it?

Question: What's small like a mouse but protects like a lion?

Question: If there were ten fish in an enclosed tank, and four swam away, three died, and three drowned, how many fish would be left?

Question: I'm priceless, and cannot be bought, Some seek my purpose, Others destroy me, Those who steal me gain no more, I never last forever, but can a life-time. What am I?