Correct Response: D. A scientist puts forward a hypothesis as a reasonable explanation of a natural phenomenon. The goal of a scientific investigation based on a particular hypothesis is to prove or disprove the hypothesis as a way for furthering understanding of the phenomenon being investigated. Answering a question that was addressed by previously completed research (A) does not require a scientific investigation. While the hypothesis underlying a scientific investigation may affect the investigation's design, it does not provide a format that outlines what particular approach should be used (B). A summary of existing research on the topic (C) is useful for developing a hypothesis, but it is not in itself a hypothesis.
