Consumers usually save the most money on major purchases when they

agree to an installment plan.
save up to pay with cash.
take out a low-interest loan.
agree to rent to own.

save up to pay with cash.

When consumers save up and pay something with cash, their responsibilities towards the seller end immediately. However, in any other situation, the buyer remains tied to the seller (or the bank) until the full amount has been paid. This often leads to the buyer spending much more than he intended. It also leaves him vulnerable to extra charges such as interests.

i think it may be b, i'm not exactly too sure on this. but b seems to make more sense.

the correct answer is (a) . answer should be simple, clear and brief.