Guessing from context

Consider the image below. What object is hidden behind the grey box?

Choose from the available list of categories below:

Enter up to four guesses and then click submit. If you enter one guess and it is correct, you get one point. If you enter two guesses and one of them is correct, you get 1/2 points. If you enter three, you get 1/3 points, and if you enter four you get 1/4 points. Incorrect guesses are worth zero points.