T.J. has a fitness goal to increase his cardiovascular fitness level. Based on training principles, what should T.J. do to work toward that goal?

A) He should start participating in shot put and discus throw on the school's track team. This requires him to start a weight training program.

B) He should start a stretching program that requires him to stretch every morning. This will increase his flexibility.

C) He should start lifting weights for an hour a day, three days a week. After the first month, he will add in some stretching and add walking for 10 minutes before each workout.

D) He should start walking two miles a day, three days a week. After two weeks, he will jog one mile and walk one mile three days a week.