Answer:
c
Explanation:
because it has made its way to the bottom meaning its been their longer
its not a b/c it on top and hasn't had enough time to break down
its not b b/c well theres nothing their
In an experiment, the group of test subjects left untreated or unexposed to some procedure and then compared with treated subjects in order to validate the results of the test
Answer:
A and D i think
Oxygen is ONLY released and others are taken in.
Gas exchange during respiration occurs primarily through diffusion. Diffusion is a process in which transport is driven by a concentration gradient. Gas molecules move from a region of high concentration to a region of low concentration.