Notice that the variables are the number of household online-devices and the number of people in the household. But, the number of devices and the number of people can't be a decimal or a fraction because they can't be divided into parts. So, they must be represented by whole numbers, not integers. The reason of this is beacuse whole numbers are just positive numbers including the number zero, while integers include negative numbers and the numbers of devices and the numbers of people can't be negative.
Therefore, the correct answer is whole numbers.