Which set of ordered pairs represents a function? A. {(-1.5, 3), (-2.5, 3), (0, 3), (3.5, 3)}
B. {(2, 12), (6, 15), (-2, -1), (6, 3), (8, 8)}
C. {(7, 1), (7, -1), (5, 2), (5, -2), (3, 3)}
D. {(1.2, 3), (2.2, 4), (3.2, 5), (3.2, 6)}

When rates are expressed as a quantity of 1, such as 2 feet per second or 5 miles per hour, they are called unit rates. if you have a multiple-unit rate such as 120 students for every 3 buses, and want to find the single-unit rate, write a ratio equal to the multiple-unit rate with 1 as the second term.