Growing crops uses water. Put these foods in order from least water usage to most water usage (per pound grown):
Milk Corn Beef Tomatoes

Milk Corn Tomatoes Beef

Explanation:

The water footprint is defined as the water usage by organisms or species.

Water is the most important source to grow food. Foods in order from least water usage to most  water usage (per pound grown) are as follows:

Milk uses the least water during its production as it requires 4.5 pounds of water to produce one pound of milk. Corn uses more water than milk as it will dehydrate if they not get proper water supply. Tomatoes are the vegetable that takes the most of the water to grow. Meat or beef requires the highest amount of water to produce.

Hence, the correct answer is "Milk Corn Tomatoes Beef".