Good Riddles

Question: How do you tell if a snake is venomous or not?

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?

Question: I'll amuse you for an entire evening, But you won't remember me. What am I?