Correct Answer: C

Rationale: The passage suggests that more studies are needed to determine the true benefits of aromatherapy.

Correct Answer: A

Rationale: The tone is appreciative of the work and impact of the CDC over time.

Correct Answer: B

Rationale: The tone is uncertain because the author raises questions about the efficacy of aromatherapy.

Correct Answer: D

Rationale: The passage does not mention the divisions that make up the current CDC.

Correct Answer: A

Rationale: The passage discusses the long-term effects of environmental toxins, which aligns with this main idea.