A convex lens is used as a simple microscope in two ways: (i) with the final image at infinity (normal adjustment) and (ii) with the final image at the near point D. How does the magnifying power change when the adjustment is shifted from case (i) to case (ii)?
a) It remains unchanged.
b) It increases by fD.
c) It increases by 1.
d) It decreases by 1.