Which of the following statements best describes the difference between the black-box and the white-box approaches to test-data design?

a. The black-box approach relies on knowledge of the functional specifications of the program to be tested, whereas the white-box approach relies on knowledge of the program's internal structure

b. The black-box approach emphasizes reliable test-data design, whereas the white-box approach emphasizes cost-effective test-data design

c. The black-box approach is oriented toward automatic test data generation, whereas the white-box approach is oriented toward automatic theorem proving

d. The black-box approach is oriented toward unit testing, whereas the whitebox approach is oriented toward system testing