The correct option is C 18
The general form of abc is 100a+10b+c.
The general form of cba is 100c+10b+a.
Now, (abc- cba) = (100a+10b+c) – (100c+10b+a) =99a-99c
= 99(a – c)
Now, abc – cba is divisible by 99, because 99 is the factor of abc – cba.
So, all the numbers which are the factors of 99 will also be divisible by abc-cba.
Here, 9, 11 and 33 are the factors of 99. But 18 is not a factor of 99. Hence abc- cba is not divisible by 18.