20. Exponential and Logarithmic Functions

Which of the following is the graph of a one-to-one function?

Which of the following is the graph of a one-to-one function?

Consider the following relations. Which is a one-to-one function?

Consider the set of ordered pairs. Verify if it is one-to-one. If so, find its inverse.

$f=\left\{\right(2,9),(4,11),(6,15),(8,20\left)\right\}$