D. The body will be able to produce the antibodies and memory cells needed to fight disease and recover quickly. Exercise and vitamin C is what creates antibodies and white blood cells that fight diseases. Plus exercise can clear the lungs of any dangerous germs that can cause illness like a cold or flu. And sleeping well and resting would remove any kind of stress one would receive from exercising.
A food chain is a single line of organisms, where each is preceded by something that it consumes and is followed by something that consumes it. A food web branches out in all directions with arrows pointing from organisms to any number of organisms that consume it.