Which of the following numbers could be used to specify how many cups of flour should be used in a bread recipe?

1, 2, 3, 4, 5

The numbers that can be used to specify how many cups of flour should be used in a bread recipe can be any positive whole number or fraction. Some common measurements for flour in bread recipes include 1 cup, 1/2 cup, 1/4 cup, and so on. It ultimately depends on the specific recipe and the desired quantity of bread you want to make.