Step 1: Understanding the Concept:
This analogy is based on a cause-and-effect relationship. One word is a substance or agent, and the other is the quality or state it produces.
Step 2: Detailed Explanation:
The relationship is: An EMOLLIENT is a substance that causes or promotes SUPPLENESS (softness and flexibility).
We need to find an option with the same cause-and-effect relationship.
(A) An unguent is an ointment; it might increase elasticity, but that's not its primary defining purpose in the same way an emollient's is to create suppleness.
(B) A precipitant causes a substance to precipitate (form a solid), not cause absorption.
(C) An additive is something added, but it doesn't necessarily cause fusion (joining together).
(D) A DESICCANT is a substance that causes or promotes DRYNESS (by absorbing moisture). This relationship perfectly mirrors the original pair.
(E) A retardant is a substance that slows down a process; it decreases, not promotes, things like permeability or flammability.
Step 3: Final Answer:
The relationship "A is a substance that causes the state of B" is consistent between "EMOLLIENT: SUPPLENESS" and "DESICCANT: DRYNESS." Therefore, option (D) is the correct answer.