When Alex was about 2 he started asking me why I had to go to work. Trying to keep it simple I explained that I went to work so we could get food to eat. Since then he's asked me time and time again. We'll be sitting down to breakfast and he says "Daddy, why do you have to go to work?" I respond "To get us food." and he smiles and says "OK".
On Sunday I was preparing to go away on a business trip. I told Alex that I was going to work and wouldn't be home for a few days. Alex thought about this for a second and then asked "What kind of food are you going to bring home?"