Choose the multiple choice answer and provide an explanation:
1) Which of the following is an example of a multiple-level total?
a. A total shown at the end of the report for the number of books in a library.
b. A total shown every time the type of book changes (for example, reference, fiction, nonfiction).
c. A total shown at the end of the report for the number of books in a library and the number of books on loan.
d. A total shown every time the type of book changes (for example, reference, fiction, nonfiction), as well as a total at the end of the report for the number of books in the library.