Which of the relations given by the following sets of ordered pairs is a function?
a. {(10)}
b. {(2,−,−3,,−5,3)}
c. {(1,−,−,,,5)}
d. {(−2,,−4,,,−6)}

Functions cannot have the same X value (the first number), but they can have the same Y value (the second number).
A. {(1,2),(2,3),(3,4),(2,1),(1,0)}
B. {(2,−8),(6,4),(−3,9),(2,0),(−5,3)}
C. {(1,−3),(1,−1),(1,1),(1,3),(1,5)}
D. {(−2,5),(7,5),(−4,0),(3,1),(0,−6)}

Choice A. has two repeating X values [(1,2) and (1,0), (2,3) and (2,1)]
Choice B. has one repeating X value [(2, -8) and (2,0)]
Choice C. all has a repeating X value (1)
Choice D doesn't have any repeating X values.

In short, your answer would be choice D [{(−2,5),(7,5),(−4,0),(3,1),(0,−6)}] because it does not have any repeating X values.