Choose set of numbers from the four alternatives sets that is similar to the given set.

(8, 12, 18)

(7, 11, 17)

Pattern followed here is :-

( 8 , 12 , 18 )

8 --->(+4) = 12  --->(+6) = 18

By solving one by one for each option,

( 6 , 12 , 18 )

6 --->(+6) = 12  --->(+6) = 18

Not followed

( 7,11,15)

7 --->(+4) = 11  --->(+4) = 15

Not followed

( 7 , 11, 17 )

7 --->(+4) = 11  --->(+6) = 17

followed

( 9 , 13 , 20 )

9  --->(+4) = 13  --->(+7) = 20

Not followed