<span>Oxygen from the inhaled air diffuses through the walls of the alveoli
and adjacent capillaries into the red blood cells. The oxygen is then
carried by the blood to the body tissues. Carbon dioxide produced by the
body's metabolism returns to the lung via the blood.</span>
Answer:
The correct option is letter B. There are other possible explanations for his results.
Explanation:
One possible explanation for the results, for instance, is the fact that all the students have already taken the same tests before. It is okay to use the same tests again but, since students already know it, they could figure out a way to do better this time. For Mr. Jacobs to be sure of his results, he should have divided his students into two groups. One group would train according to the new program and the other group wouldn't. They would be tested and have their results compared. If the experimental group - the one that used the new program - did better than the control group, then Mr. Jacobs could conclude the program works.
