Which of the following relations is not a function?

A. { (0,1), (1,1), (2,1), (3,1)}
B. { (0,0), (3,4), (5,6), (8,9)}
C. { (0,1), (0,2), (0,3), 0,4)}
D. { (0,0), (2,2), (4,4), (6,6)}

15. jiovanni is looking in to two different companies that offer study guides for math exams.test prep 101 charges a $5 flat fee and an additional $0.25 per problem.math charges a $2 flat fee and an additional $0.50 per problem.how many prablems would make the costs of the two companies be equal? varibles: equations/eniqualities{ {