only one complete image is formed...........so the correct option is c)........

this is because........to form an image u need jus two rays of light to intersect at the pt..........the more the no. of intersecting rays the more bright will be the image as it involves a higher intensity............

but by closing the middle portion u wud prevent some of the rays frm passing thru the lens.........due to which the intensity will decrease thus making the image look less brighter..........