Match List-I with List-II and select the answer using the codes given below the Lists: List-I (Symbol of element): A. Sm, B. Cs, C. Os, D. Np. List-II (Group of element): 1. Transition element, 2. Alkali metal, 3. Actinoid element, 4. Lanthanoid element. Codes: A B C D

Samarium (Sm) has atomic number 62 and belongs to the lanthanoid series (A-4). Caesium (Cs) is a Group 1 element, an alkali metal (B-2). Osmium (Os) is a d-block transition element belonging to Group 8 (C-1). Neptunium (Np) is element 93 and belongs to the actinoid series (D-3). Therefore, the correct matching is A-4, B-2, C-1, D-3, corresponding to option (a).