A bag contains red apples and yellow apples. The ratio of red apples to yellow apples in the bag is 9 to 4. Which of these statements could be true?
A There are exactly 6 red apples and 1 yellow apple in the bag.
B There are exactly 18 red apples and 8 yellow apples in the bag.
C There are exactly 4 red apples and 9 yellow apples in the bag.
OD There are exactly 9 red apples and 13 yellow apples in the bag.