C
because you would take 3/4 and multiply it by 3/3 to get the denominator to 12
and you would multiply 1/3 by 4/4 again to get the denominator to 12.
You are getting the denominator to 12 because 12 is 3 and 4s Most Common multiple!
Now that you have multiplied them you should have 9/12 and 4/12
Then you subtract 4 from 9 to get 5.
So the answer is 5/12!