Which set of ordered pairs represents a function?

\{(-4, -2), (4, 1), (4, -7), (-2, 3)\}{(−4,−,,−−2,3)}
\{(-9, -2), (5, -6), (-4, 3), (5, 2)\}{(−9,−,−−4,,2)}
\{(-8, 0), (-4, -9), (-6, -1), (2, -1)\}{(−8,−4,−−6,−,−1)}
\{(5, -7), (1, 4), (7, -3), (1, -8)\}{(5,−,,−,−8)}

"you know, playing tennis is healthier than watching a tennis match on television," katya remarked to her couch potato brother. in this sentence, healthier is a/an a. superlative. b. comparative. c. positive form. d. adverb.

Arestaurant offers a $12 dinner special that has 5 choices for an appetizer, 12 choices for an entrée, and 4 choices for a dessert. how many different meals are available when you select an appetizer, an entrée, and a dessert? a meal can be chosen in nothing ways. (type a whole number.)

Which expression can be used to determine the slope of the line that passes through the points -6, three and one, -9