the verticle line test is if you draw a line at x=(insert x-value in question) and it hits more than two points from that equation then that does not pass the verticle line test. In the picture I attached, the green funtion(circle) does not pass the verticle line test because it hits x=1(black line) in more than one place while the red function(exponential function) passes the verticle line test because it hits x=1 at only one point.
the correct answer would be A. the mean is when you add up all of them and divide it by how many numbers there are which in this case is 5. and the median is the number in the middle, in this case 20, therefore when you add up all numbers in A ,you get 105 and you divide it by 5 which gives you 21. :))