The inferences I can make regarding the pH of a particular part of the digestive system is that it has a pH of 3. I know that 7 is neutral, and 8-14 is basic. I know that below 7 is acidic. The lower the number is from 7, the more acidic it is. I know that hydrochloric acid is quite acidic because I feel the burn from it when I get acid reflux attacks. I think the relative size of carbon-based molecules are the size of a nickel, which I think is quite large. I think this because humans need carbon to live and a lot of foods contain carbon, so a lot of carbon molecules are broken down in the digestive tract.