Good Riddles

Question: If it's information you seek, come and see me.
If it's pairs of letters you need, I have consecutively three.

Who am I?

Question: Smell me, buy me, and deliver me.
I won't change.

What am I?

Question: A man wants to have a party in thirty-one days where he will be serving his 1000 barrels of wine. The only problem is that one of his enemies poisoned one of the barrels. The poison kills any man who drinks any of the wine in about 30 days, give or take a few hours. The man has 10 plants that are also killed by the poison in 30 days and can be used to test the wine. How can identify the single poisoned barrel of wine?

Question: A natural state, I'm sought by all.
Go without me, and you shall fall.
You do me when you spend,
and use me when you eat to no end.

What am I?

Question:

You have a large number of friends coming over and they all get thirsty. Your first friend asks for 1/2 a cup of water. Your second friend asks for 1/4 a cup of water. Your third friend asks for 1/8 a cup of water, etc.

How many cups of water do you need to serve your friends?