According to the american college of sports medicine (in 2011) you need to exercise around 30 + minutes a day (150 minutes a week) to lose a "modest" amount of weight.
I believe the answer is D mainly based off the wording. The question says "Devices" And the only answer with devices involved would be D, Personal protective equipment.
“Cellular respiration is a set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP) and then release waste products”
Exercise, therapy, or get a new hobby to distract you