Good Riddles

Question: What is that thing we buy for eating but cannot eat it?

Question: What is the center of gravity?

Question: What has 3 feet but cannot walk?

Question: There are 3 stoves. A glass stove, a brick stove , and a wood stove. You only have 1 match. Which do you light up first?

Question: I'm written with two letters, said with one and seen with two.What am I?