Which of the following statements are not true regarding functions? check all that apply. a.) the vertical line test may be used to determine whether a function is one-to-one. b.) a function is a relation in which each value of the input variable is paired with at least one value of the output variable. c.) the horizontal line test may be used to determine whether a function is one-to-one d.) a sequence is a function whoes domain is the set of natural numbers.