Question

Which graph represents a function?

On a coordinate plane, a straight vertical line crosses the y-axis 0 times and the x-axis 1 time.

On a coordinate plane, a curved line crosses the y-axis 2 times and the x-axis 1 time.

On a coordinate plane, 2 curved lines are shown. Both lines touch the y-axis 1 time and the x-axis 1 time.

On a coordinate plane, a straight horizontal line crosses the y-axis 1 time and the x-axis 0 times.

Answer 1

use the vertical line test (if *any* vertical line can be drawn such that it crosses the graph multiple times, it's not a function)