A converging lens is used to form an image on a 
screen. When the upper half of the lens is convered by 
an opaque, screen then 
a) Half the image will disappear 
b) Complete image will be formed
c) Intensity of the image will decrease
d) Intensity of image will increase.

As upper half is covered, intensity of upper half part will not reach at the image, so intensity of image will decrease but image will be formed because there are many rays from the lower half which completes the image. So, intensity of the image will decrease and no part of image will disappear.