First we have to find how many chose cat:
100-48-14-2= 36%. Because the whole thing is 100% and I removed all the other animals to find the percentage of cats chosen.
Then we want to know the number of classmates:
Cat= 36% of 50 people = 0.36 x 50=18
Fish= 14% of 50 people = 0.14 x 50= 7
Now we see the difference between them :
18-7=11 people
The answer is D which is 11.