Exercising with a partner will likely make it
a. more difficult to make a commitment to exercise
b. less enjoyable to exercise
c. easier to stick to an exercise program
d. difficult to agree on an exercise program

C. Easier to stick to an exercise program. When you have multiple choice questions it's easier to discard the options one by one until you have just one left. The main problem for most people to exercise at home is that it could be boring and you don't have anybody watching you and at the end you either don't do a complete routine or skip days. That's why you pay for a gym, where you force yourself to do the exercise. You solve all those problems finding somebody else who wants to exercise too so you two share an exercise program. For those reasons you can easily discard A, B and D.