kids say the darnest things

In my 4th grade science class on Thursday we were reviewing matter- states, properties, etc. I was with a group of 4 students and they sort of got off topic, but we went with it. I am a solid, said one kid. Another replied, well you have liquid too. What's a liquid in the body? I asked. Blood they all shouted. Then one kid goes, you know why your blood is red? why? I replied. Your blood is red because of all the tomatoes we eat! another kid answered, I don't eat tomatoes, to which the response was, but you eat ketchup! Then another kid (surprisingly got us back on topic) asked there's air in your body too? correct I said. What about your brain? another kid asked? what's your brain? best answer of the day: your brain is air, mine is like a sponge! haha I couldn't help but laugh when I heard a 4th grader answer this- all in English!! I had to reply that yes, some people do have lots of air in their heads.