Please help, this is an exam question!
Jose walks briskly for at least 15 minutes, four days a week. In about six weeks, Jose will have daily marching band practices that will last three to four hours, and he wants to make sure he is physically ready. What would be the best way for Jose to apply the principle of progression to his routine?
A.) Increase the duration of his walking each day
B.) Add swimming to his current fitness routine
C.) Carry a heavy backpack while walking
D.) Alternate between a treadmill and walking outside