4. Using valid and reliable sources when doing research is essential because

A) students often fail to differentiate between valid and invalid sources.

B) it is the most proven of all known research methods.

C) it makes the citation process more efficient.

D) incorrect information can invalidate the conclusions.

4. The correct choice is D.

The question is asking why valid and reliable sources are important, so the answer must address this point directly. Neither the fact that students have problems telling the difference between sources nor the ease of citations explains the impact of poor sources on research. The problem created by invalid sources manifests in the conclusions derived from the research. Since only D addresses the problems created by poor sources, it is the correct answer.