Four combinations of two thin lenses are given in List I. The radius of curvature of all curved surfaces is r and the refractive index of all the lenses is 1.5. Match lens combinations in List I with their focal length in List II and select the correct answer using the code given below the lists. List I List II P. Q. R. S. Code: (A) P-1, Q-2, R-3, S-4 (C) P-4, Q-1, R-2, S-3 1. 2r 2. r/2 3. -r 4. r (B) P-2, Q-4, R-3, S-1 (D) P-2, Q-1, R-3, S-4