A series is given, with one number/letter missing. Choose the corrects alternative from the given ones that will complete the series. 15, 39, 74, 122, ?, 265

Finding the pattern in differences: 39-15=24, 74-39=35, 122-74=48. The second differences are: 35-24=11, 48-35=13. The second differences increase by 2 each time (11, 13, 15, 17...). So next first difference should be 48+15=63. Adding to last term: 122+63=185. Verification: Next difference would be 63+17=80, giving 185+80=265, which matches the final term. Option A (171) would require difference of 49, breaking the pattern. Option C (151) would require difference of 29, breaking the pattern. Option D (165) would require difference of 43, breaking the pattern. Option B (185) correctly fits.