Select the option in which numbers are related in the same way as are the numbers of following set. (15,  20,  24)

(11, 16, 20) (9, 14, 19) (17, 23, 26) (21, 26, 29)

(11, 16, 20)

15  →  +5  →  20  →  +4  →  24   Similarly, 11  →  +5  →  16  →  +4  →  20   So, correct answer is (1).