Jesse notices that his gas mileage jumps from 20 to 40 per gallon when he uses his cruise control. one likely explanation for this is: a. jesse's car is powered by a biofuel that is not needed while cruising b. jesse's car is compressing and expanding efficiently c. jesse's car has an efficient air-to-fuel ratio d. jesse's car is a hybrid that shuts off extra pistons when it is not accelerating

You exhale co2 which is produced during cellular respiration.  co2 combines with the water in your blood's plasma to make up one half of the body's most important buffer pair, carbonic acid.  the more physical activity you engage in, the more co2 your body is producing.  you can see this by putting some of the cabbage indicator in a glass and then blowing bubbles into it through a straw.  can you see a change in the color of the indicator?