Answer:
A. m - 7.
Explanation:
The phrase "The difference between the number of magic markers and 7 colored pencils" means you are subtracting 7 colored pencils from the number of magic markers.
So, if "m" represents the number of magic markers, the expression "m - 7" indicates that you are taking the number of magic markers (m) and subtracting 7 from it, which is exactly what the phrase describes. That's why the correct choice is A. m - 7.