Answer:
they did the horizontal line test.
Step-by-step explanation:
the vertical line test is to see whether or not a graph is a function. you can draw a vertical line at every x-value to see if there are 2 or more points at that x-value. if there are, then it is not a function. however, this student drew a horizontal line instead. this graph is a function, so the student is incorrect. they did the horizontal line test instead of the vertical line test.
