Every fitness program should include a. at least 60 minutes of cardio activity. b. a warm-up, a primary conditioning period, and a cool-down. c. at least 15 minutes of vigorous activity. d. a longer warm-up period than cool-down period

I'd personally say B because a warmup will reduce injury, soreness, and get you ready. Then you have your exercise. Then the cooldown helps bring the heartrate down to near-normal and to get the blood circulating freely back to the heart. Stopping abruptly could result in fainting or place undue stress on the heart.

Ibelieve the correct answer is  stratum  lucidum.