Correct option is C
In this question following logic is followed-
1st + 2nd = 3rd Number
8, 13, 21 → 8 + 13 = 21
13, 18, 31 → 13 + 18 = 31
Similarly,
Option (a) (14, 19, 33) → 14 + 19 = 33
Option (b) (8, 3, 11) → 8 + 3 = 11
Option (c) (11, 16, 29) → 11 + 16 = 27 ≠ 29
Option (d) (17, 12, 29) → 17 + 12 = 29
Therefore, the correct answer is (c).