Respuesta :
The right option is; B.) progression
Progression principle is at work in this situation
Progression is a basic training principle which describes how an individual can achieve an optimal level of overload, and also the ideal period for the overload to take place. Progression is demonstrated during training when either frequency, intensity, or time or the combination of the three is gradually increased. From the question, the progression principle is at work because Stacy keeps adding distance in intensity to progress her train runs.