Stress is
a. positive or negative, depending on circumstances
b. a body's automatic physical response
c. a negative reaction to outside influences
d. a and b only

The human body automatically reacts to stress encountered in the outside world. Depending on how the person handles the stress, it can be a positive or negative effect. Stress is designed to enable the body to fight and operate under tough circumstances. In today's world, some people take on the burden of too much stress and it can end up being harmful to the body.

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.