To study the variations, in current flowing, in a circuit containing a LDR, because of a variation.
(a) in the power of the incandescent lamp, used to 'illuminate' the MR. (Keeping all the lamps at a fixed distance).
(b) in the distance of a incandescent lamp, (of fixed power), used to 'illuminate' the LDR.

This is a good site for any  hard questions and to be give best solution for us