Answer:
D. y = 3x+1
Step-by-step explanation:
A -- this describes the inverse function rule (x and y are interchanged).
B -- this describes one point that is described by the function rule, but does not cover the remaining infinite number of points.
C -- there is no variable y in the right side of the rule, so this would give f(1) = 3x+1, f(2) = 3x+1, and so on. The value will always be "3x+1" for any function argument. This is not the same as the given function rule.
D -- y (or any other variable except x) can stand in for f(x), so this is the same as y = f(x). It is another way to write the function rule.
