I didn't notice this when I first took this quiz before, but today, when I took the quiz for the second time, it caught my eye.  When I go to answer other questions of the quiz when I click on any of the four options if the option is correct there is a green signal but if I click on the wrong option then there is a red signal but when I click on this question there is no signal.  (green and red). I am very interested to know what the secret behind this could be.