Which number is not composite 2,9,15,21

Of the following, which statement or statements accurately reflect a way in which credit can be safer than cash? i. if your credit card gets stolen, you can cancel it and get your money back. ii. it is harder to lose a single credit card than a large number of bills. iii. if a merchant does not honor the agreement, you can call the credit company and dispute the charges. a. i and iii b. ii only c. iii only d. i, ii, and iii