Answer:
The first one. The single line
Step-by-step explanation:
I can explain later but since you need it quick I will send my answer now :3
Further explanation:
A function is only a function if there are two x values to a single y value.
You can use the "vertical line test" to find out if a function is a function or not.
The vertical line test is where you put a line vertically through the function.
If at any point along the vertical line the function touches the line more than once, then it is not a function.
