Which describes radioactive decay of a substance? 1) more of the radioactivity is lost during the first half-life than in later half-lives. 2) more of the radioactivity is lost during the fourth half-life than in the first half-life. 3) isotopes are the most stable during the first half-life. 4) isotopes are the least stable during the later half-lives.

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?