Persia is motivated to show she is more limber on her President's Challenge sit and reach test. For the past 6 weeks she has been doing a stretching routine 4 days per week that includes 12 different stretches which she holds for 20 seconds each. A change to her program would indicate she is using the time principle to increase her flexibility when she increases her: (2 points)

Group of answer choices

A. holding time to 25 seconds each

B. number of specific core stretch exercises

C. range of motion for each stretch

D. stretching to 5 days per week