the correct answer for this is a 3:4 ratio
reason: 12:16 can be simplified in different ways, to find the ratio you must find a number that both 12 and 16 are divisible by, to find this number that they are both able to be divided by, you have to try dividing them by different numbers. 12 can be divided by 4, this equals 3. 16 can also be divided by 4, this equals 4. Therefore the correct answer is a 3:4 ratio.
hope this helps :)