Which research model refers to the study of an individual, group, or community over a predetermined period?

answer: my answer would be a) scheduling workouts with your friend for consistent days and time

explanation: for me personally i would be much more likely to go to the gym with a friend because i wouldn't want to cancel on them or stand them up.

                                                        water

a colorless, transparent, odorless, tasteless liquid that forms the seas, lakes, rivers, and rain and is the basis of the fluids of living organisms.

                                                        halon  

any of a number of unreactive gaseous compounds of carbon with bromine and other halogens, used in fire extinguishers, but now known to damage the ozone layer.

                                                  dry chemical

extinguishing agent used on class a, class b, and class c fires.

                                                  carbon dioxide

a colorless, odorless gas produced by burning carbon and organic compounds and by respiration. it is naturally present in air (about 0.03 percent) and is absorbed by plants in photosynthesis.