C & D are only part of the question and unsuitable, so it's either A or B, but I'd say it's more likely A~<span> How does changing the amount of water affect the growth of corn? </span>
The correct answer is: A. How does changing the amount of water affect the growth of corn?
While options B, C & D are not impossible to test, option A is the only question that can be tested using quantitative methods, such as statistical analysis. The question in option A states: "How does changing the amount of water affect the growth of corn?". This question is easily testable using scientific investigation, because controlled or measured amounts of water can be added to corn, and the consequent growth rate of corn can be easily measured and recorded. However, the questions in options B, C & D cannot be precisely measured using quantitative tools, since they aim to measure qualitative (subjective) factors, such as: ethics, happiness and disappointment.
The mantle is the mostly-solid bulk of Earth's interior. The mantle lies between Earth's dense, super-heated core and its thin outer layer, the crust. The mantle is about 2,900 kilometers thick, and makes up 84% of Earth's total volume.
usually in association with myosin, are responsible for many types of cell movements. Myosin is the prototype of a molecular motor—a protein that converts chemical energy in the form of ATP to mechanical energy, thus generating force and movement.
