Which of the following best defines an input? a. an input is the result of a relation or the function rule, usually the y-values in a set of ordered pairs or on a table or graph. b. an input is a special type of relation for which there is a rule that pairs each input with exactly one output. c. an input is a set of ordered pairs in which no y-value repeats. d. an input is the value that determines another based on the relation or the function rule, usually the x-values in a set of ordered pairs or on a table or graph.