A convex lens' \(A^{\prime}\) 'of focal length \(20 \mathrm{~cm}\) and a concave lens' \(B\) ' of focal length \(5 \mathrm{~cm}\) are kept along the same axis with a distance ' \(d\) ' between them. If a paralle beam of light falling on' \(A^{\prime}\) leaves ' \(B\) ' as a parallel beam, then the cistance ' \(d\) ' in cm will be:
A 25
(B) 15
c 50
(D) 30
