To be effective, an exercise program must be?

To be effective, an exercise program must have an aerobic form, portion for strength enhancement, and a stretching part. These three things are essential because they each target specific improvements in your body. For example, aerobics can help you maintain your body’s fitness or make it better. This usually targets your heart rate and ensures that you burn fat while doing so. Second is strength enhancement; this will make sure that your body becomes better – not just in a feeble state. Lastly is stretching, your muscles are like rubber bands. You cannot end or start your exercise program without stretching simply because they can damage your muscles as well. Aside from this, stretching can stop you from shocking your body into a physical activity, which may cause you to lose consciousness or have undue stress and fatigue. 

answer; ///i believe that the correct answer is (45*) at a 45 degree check first good

i believe the answer would be:

d. violin, clarinet, french horn, and tuba