Answer:
b. he works hard enough to keep his heart beating fast
Explanation:
Moderate or vigorous physical activity is synonymous with moving muscles. The more muscle fibers strive to accomplish a task, the more they consume the oxygen brought into the bloodstream. This forces the lungs to work at a fast pace, as they are responsible for oxygenation. The heart also speeds up because it needs to pump blood more vigorously. This is why, while exercising, your heart rate and breathing rate must increase.
With that, we can say that for Shane to use his garage cleaning as a vigorous or moderate physical activity he will have to move to the point of keeping his heart beating fast.
