Answer: C. Grow the tree in a pot and measure the mass of the soil before and after the tree grows to a certain height
Explanation: When testing an hypothesis, which is a prediction of the outcome of an experiment, it is vital to keep all other factors, that can affect the outcome of the experiment, constant; so that any outcome can be attributed (or disregarded) to the variable being tested.
In this case, the variable being tested is the soil, and so all other factors such as water, air, sunlight, etc. should be kept constant.
Answer:
They went on the Oregon Trail.
I think it's D because "Causation" is <span>the action of causing something.</span>
