Understanding "Pertinent"
The term "pertinent" refers to something that is relevant or applicable to a particular matter or situation. To grasp why "inappropriate" is considered the correct answer in this context, let's evaluate the options provided.

Options Analysis
- a) Germane
- This term means relevant or fitting. It is synonymous with "pertinent."
- b) Apposite
- This word also conveys the meaning of being appropriate or relevant to the situation at hand, aligning closely with "pertinent."
- c) Apropos
- Similar to the above, "apropos" means relevant or appropriate in relation to something else. It supports the idea of being pertinent.
- d) Inappropriate
- This term means not proper or suitable in the circumstances. It directly contradicts the meaning of "pertinent" as it indicates a lack of relevance or suitability.

Conclusion
Given the definitions, options A, B, and C all denote relevance or appropriateness, while option D, "inappropriate," implies irrelevance. Thus, the correct choice is indeed option 'D,' as it stands in stark contrast to the meaning of "pertinent." Understanding these distinctions is crucial for GMAT verbal reasoning, where precise word meanings can make a significant difference in answering questions correctly.