At a regular routine checkup, hilda’s doctor tells her that her eight-month-old daughter has now gained object permanence. what is her doctor referring to?

The doctor is referring to the ability to realize things are still there even if not seen.

Object permanence is the understanding that objects continue to exist even when they cannot be perceived.

The person who utilize the progression principle will keep adding the difficulty of the exercise that he's doing, while the person who does not, will only stay stagnant.  the person that utilize progression principle, will get a stronger endurance because now his body is conditioned to do harsher routines.{the answer was already on verified)