Sheesh agree with that person^ bc i personally don’t knowww
D. doesn't lead to a productive end.
Muscular strength
in case you didn't know the definition of muscular strength, you could use process of elimination. it's not muscular endurance because endurance is testing how long you can do something over a period of time, and the question is asking about all at once. it's not flexibility or body composition because neither are testing how much force your body can exert. that leaves muscular strength.
A cool down routine is important after exercise because it helps to bring your heart rate down to a normal level after increasing it during exercise.