In order to find the next day that the quizzes will be due again, we first need to find the least common multiple (LCM) of the numbers 4 and 3.
To do so, we first need to factorate each number:
Then, we multiply each factor the maximum number of times they appear. In this case, we need to multiply 2 two times and 3 one time:
So the LCM is 12. Now, we just need to add 12 days to the last due date, which was 7 December. Adding 12 days, the next due date will be 19 December.
So the answer is C.