Which of the following is the best example of vigorous activity, as opposed to a moderate activity?

Well you haven't provided any answer options so answer options include things like mountain climbing. Mountain climbing involves multiple systems and functions over a long period, with moderate being something like hiking the same mountain.

Well if you pick a machine to work on and that's gonna be your exercise if you don't stick to that machine your muscle strength your muscle mass rather will change because you haven't been doing it you change something in your exercise routine which changes your body's form of dealing with things for example you might become weaker or stronger depending on what kind of exercises you do in whether or not the machine you picked actually your muscles grow.

The answer is epidermis