Identifying Tables that Represent Functions

Which table, the table, the table, or the table, represents a function (if any)?

$$\begin{array}{cc}\text{Input}& \text{Output}\\ \text{2}& \text{1}\\ \text{5}& \text{3}\\ \text{8}& \text{6}\end{array}$$

$$\begin{array}{cc}\text{Input}& \text{Output}\\ \text{–3}& \text{5}\\ \text{0}& \text{1}\\ \text{4}& \text{5}\end{array}$$

$$\begin{array}{cc}\text{Input}& \text{Output}\\ \text{1}& \text{0}\\ \text{5}& \text{2}\\ \text{5}& \text{4}\end{array}$$

OpenStax, Algebra and Trigonometry 2e · §3.1 Functions and Function Notation · Example 4