When John first bought his new house,he could mow the yard in the morning and then go for a run in the afternoon.John,who is now in his late fifties,finds that mowing the yard completely wipes him out for the day.John is experiencing a decline in his

A) reserve stamina.
B) reserve capacity.
C) reserve capability.
D) reserve oxygen supply.

Reserve Capacity

The extra, unused ability or resource that individuals can draw upon in times of need or stress, contributing to resilience.

Reserve Stamina

The extra capacity or energy that an individual can draw upon when needed, beyond what is normally utilized in daily activities.

Reserve Oxygen Supply

The additional quantity of oxygen kept in reserve, often in the muscles or blood, that can be utilized during intense physical activity or when normal breathing is insufficient.