Select the set in which the numbers are related in the same way as are the numbers of the following set.

7 — 14 — 23

4 — 11 — 20

NOTE: Operations should be performed on the whole numbers, without breaking down the numbers into its constituent digits. E.g. 13 – Operations on 13 such as adding/subtracting/multiplying etc. to 13 can be performed. Breaking down 13 into1 and 3 and then performing mathematical operations on 1 and 3 is not allowed)

Given: 
7 — 14 — 23
4 — 11 — 20
Logic: The second number is obtained by adding 7 to the first number.
The third number is obtained by adding 9 to the second number.
7 → 14 (+7), 14 → 23 (+9)
4 → 11 (+7), 11 → 20 (+9)
lets analyze the options;
Option (a); 7 — 15 — 22 → (+8, +7) (Does not match)
Option (b); 15 — 30 — 20 → (+15, -10)  (Does not match)
Option (c); 5 — 12 — 21 → (+7, +9)  (Follows the pattern)
Option (d); 9 — 12 — 22 → (+3, +10)  (Does not match)
​​