Correct option is C
Analyzing the sets:
(6,12,9),(7,23,15)
For each set, there seems to be a specific relation between the numbers:
Logic: ( first number+second number)/2= third number
(6+12)/2=18/2=9
(7+23)/2=30/2=15
Similarly, c) (14, 12, 13)
(14+12)/2=26/2=13
Therefore, the correct answer is (c) 14, 12, 13.