Answer:
The correct answer is B.
Explanation:
First off, if you don't already know what's the vertical line test, you're guaranteed to get this question wrong.
The vertical line test is a visual way to figure out if the function is a function. You just draw a line anywhere on the paper, and see if it intersects on one point or more than one point. If it intersects at only one point, it's a function because at the end of the day, you can have only one output for each input.
Think of this as an actual function. For example, if you go to a vending machine, and you put a dollar in for a single bag of chips, the next time you put a dollar in, you should get only one bag of chips, or else the machine is broken. It won't function.
In this case, it's a function since each input has its own output, or it passes the vertical line test, it's good to go. It's not a linear function since it's not straight, but hey, it at least is a function.