Correct Answer - Option 3 : 31215311
Given, BLACK = 2121311 and SMART = 191311820
Consider, A = 1, B = 2, C = 3, D = 4, …… Z = 26.
BLACK = B → 2, L → 12, A → 1, C → 3, K → 11 → 2121311
SMART = S → 19, M → 13, A → 1, R → 18, T → 20 → 191311820
So, CLOCK = C → 3, L → 12, O → 15, C → 3, K → 11 → 31215311
Hence, 31215311 will be the code for CLOCK.