Answer:
The correct answer is:
It asks about a cause-and-effect relationship between two variables (A)
Explanation:
Scientific investigations are aimed as developing a hypothesis and proving the validity or not of the hypothesis developed. In order for these hypotheses to be tested, experiments must be done, and the experiments are designed based on the identification of a cause-and-effect relationship existing between two variables to be tested, where the "cause" is varied to various degrees and the "effect" of the variation is recorded. Therefore, knowing the cause-and-effect relationship will guide the experimental design, which will be aimed at manipulating the causes to see how these manipulations affect the second variable.
