Final answer:
The ratio of grape juice boxes to the total number of juice boxes is 1:5, since there are 4 grape juice boxes and a total of 20 boxes in the cooler.
Step-by-step explanation:
The question asks about the ratio of grape juice boxes to the total number of juice boxes in Karrie's mom's cooler. To find this ratio, we sum up the total number of juice boxes and then divide the number of grape juice boxes by this total. There are 4 grape, 6 fruit, and 10 orange juice boxes, yielding a total of 4 + 6 + 10 = 20 juice boxes in the cooler. Consequently, the ratio of grape juice boxes to total juice boxes is 4 grape to 20 total, which simplifies to 1:5 when both terms are divided by 4, the greatest common divisor.
Therefore, the correct answer is B. 1:5.