Increased metabolic rate due to exercise is because
a.
the body uses more calories for everyday activities
b.
toxins are removed from the body more quickly
c.
blood is better able to fight infection
d.
people with a lower metabolic rate have a higher risk of cancer

The answer to your question is A . 

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.