Suppose that you want to measure the effect of an oil spill on plant growth. For this purpose, you use three identical plants that you water daily for two weeks. One plant gets a tablespoon of engine oil added to its daily water and another gets two tablespoons of engine oil added to its daily water. The third plant is watered with plain water. You measure the height of all three plants after two weeks. What is the independent variable?

The independent variable is the "engine oil".

Explanation: For an experiment to be termed whole there should be independent and dependent variable.

Independent variable in an experiment means the variable that is being controlled.

In other word, an independent variable in an experiment is the one whose variation doesn't depend on that of another which is the engine oil.

In the experiment above "the plant* is the dependent variable because it's variation depends and will occur as a result of the engine oil.

D is the anwser

Explanation: