What training principle states that you must continue to exercise to maintain fitness?

F
I
T
T

F=frequency (how often)
i=intencity (how hard )
T=time ( how long )
T=type ( what exercise you do )

So the answer could be frequency because it tells you how often you need to exercise

Bmust be the answer, as technically all organs move, so a is incorrect. all organs are made of different types of cells, so that isn’t a problem, so c is also incorrect. human hearts are very similar to many other animals’ hearts, so d is also incorrect, yet the heart is made of muscle, which is hard to grow in the lab so it would be correct to say b