Final answer:
Testing a hypothesis in scientific investigations is linked to the goal of explaining phenomena within psychology, as it involves making predictions and conducting experiments to confirm or refute the predictive power of hypotheses.
Step-by-step explanation:
Testing a hypothesis is the third step in a scientific investigation. This critical step involves making a prediction based on the hypothesis and conducting experiments to see if the prediction holds true. The goal of psychology that this step is derived from is D. explaining. Experiments are systematic observations or measurements under controlled conditions, designed to test the validity of a hypothesis and its predictive power. A well-formulated hypothesis should be able to predict outcomes, which is a foundational aspect of the scientific method and integral to explaining phenomena.