You can use the Pythagorean theorem to answer this. The diagonal is the hypotenuse of the right triangle that is formed. So, your equation will look like (h is height):

We have to solve for h:


You can plug it into a calculator, and you get approximately 19.105. The answer closest to that is
B. So, that's your answer! Hope it helps. If anything doesn't make sense, hmu!
The attached image is the graph.
Ben - 8 years old
Ishaan - 2 years old