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

for me i have felt invisible when i was clearly struggling,or,i made a great achievement ,and,nobody took to notice me either because they just didn't see it,or,people just turned their back on me.i can see a person being invisible by choice,or,without choice like i did.the people who are invisible by choice don't try to talk to people,don't try to make friends,and,keep to themselves.i haven't been one of those people so i couldn't give you a reason.

hope this and can i get bainliest my dude : d