Love Letter

Today, just as school ended, and I was sitting and waiting for my dad to come and pick me, i got a love letter. I was just sitting and playing with my cellphone when C (let's abbreviate his name to C) walked by. He gave me an empty m&m container, and told me to open it. Then he ran off. I opened the container, and found a letter which said:

"I have wanted to tell you this for a long time, but never knew how. I really like you, and even though I am a few days late, happy valentines day. Will you be my girlfriend?"

This boy is a good friend of mine, but I really wouldn't want to be his girlfriend. I really don't want to hurt his feelings either. What should I do? What should I say?