Sentence Logic and Contextual Clues
The sentence structure relies on a contrast, signaled by the word "yet."
1 The "Downward" Force: The first part of the sentence establishes that the "steady erosion of bone density" is "inexorable" (meaning it cannot be avoided or stopped).

2 The Intervention: The second part of the sentence introduces "resistance training" as a mechanism to counter this erosion.

3 The Required Meaning: Because the sentence contrasts the "inexorable" nature of the erosion with the effect of resistance training, the missing word must describe a process that slows down or lessens the intensity of that downward slide.

Analysis of the Options
- Decelerate (E) and Retard (F): Both words mean to slow down or delay the progress of a process. In this context, both fit perfectly as they describe resistance training's ability to reduce the speed of bone density loss.
- Arrest (A): This means to stop or halt entirely. Because the passage describes the erosion as "inexorable" (inherently unstoppable), "arrest" is logically too strong for this specific context.
- Nullify (B): This means to invalidate or cancel out. This is not the correct term for a biological process involving bone density.
- Compound (C): This means to make something worse. This would create a contradiction, as the sentence presents resistance training as a helpful intervention.
- Disregard (D): This means to ignore, which does not make sense in the context of a physiological effect.