Final answer:
In the experiment, the dependent variable is the number of ears of corn produced by each plant, and it depends on the different amounts of fertilizer used, which is the independent variable.
Step-by-step explanation:
In the experiment where a farmer uses four different amounts of fertilizer on his corn plants to measure which amount produces the most ears of corn, the dependent variable is A) The number of ears of corn produced by each plant. This is because the dependent variable is the one being measured as it responds to changes in the independent variable, which in this case is B) The different amounts of fertilizer. It is essential to control other factors such as c) Amount of water, d) Height of corn plants, and other environmental conditions to ensure that any differences in the number of ears of corn are due to the amount of fertilizer and not other variables.