Final answer:
The correct method to determine which of two boxes of candy has greater mass is to weigh them both using a scale, as mass is a consistent measure of matter that doesn't change with location.
Step-by-step explanation:
To determine which candy has a greater mass out of two boxes that contain an equal number of candies, the correct method would be to weigh both boxes of candy using a scale to compare their masses. This method works because mass is a measure of the amount of matter in an object and does not vary with location, unlike weight which can change depending on gravitational pull. Counting the number of candies (option b), examining color and flavor (option c), and shaking the boxes for sound differences (option d) cannot provide you with information about the mass of the candies.