Correct option is D
In this question following logic is followed-
(1st + 2nd) ÷ 2 = 3rd Number
7, 15, 11 → (7 + 15) ÷ 2 = 22 ÷ 2 = 11
9, 19, 14 → (9 + 19) ÷ 2 = 28 ÷ 2 = 14
Similarly,
11, 23, 17 → (11 + 23) ÷ 2 = 34 ÷ 2 = 17
Therefore, the correct answer is (d).