Why do less active americans not increase their activity levels?

In general, why does a tall person have a higher basal metabolic rate than a shorter person of the same weight? a. shorter people have more skin surface area and lose heat more rapidly than a taller person. b. tall people are more active than shorter people. c. taller people have more skin surface area and lose heat more rapidly than a shorter person. d. taller people eat more protein, which takes more energy to digest. e. shorter people eat less than tall people.