Answer:
Well a function can’t be on the same one as each other so thats why the vertical line test is used.
For number 14 if you’d draw a vertical line, you’d see there would be 2 answers So that can’t be a function.
For number 15, if you draw a vertical line, none of the given have 2 questions so number 15 is a function.
Whilst in number 16 if you’d draw a vertical line, there wouldn’t be anything that have 2 answers of that overlap. So it is a function