The Logic: The "Disuse" Clue
The sentence provides a clear chain of events:
1. The Cause: Nerve damage occurred after an accident.
2. The Immediate Effect: The muscles could no longer be used.
3. The Long-term Result: Because of "disuse," the muscles underwent a specific physical change.
4. The Goal: We need a word that describes the wasting away or shrinking of body tissue due to lack of use.

The Correct Answer:
A. atrophied
- Why it works: Atrophy (verb) means to waste away, typically due to the degeneration of cells, or become vestigial during evolution. In a medical context, it is the standard term for muscles shrinking when the nerves are damaged or when a limb is immobilized (like in a cast).

Why the others fail:
- B. contracted: This describes the active shortening of a muscle to produce movement. Disuse would lead to the opposite of a healthy contraction.
- C. elongated: This means to become longer. Muscle disuse doesn't typically result in lengthening; it results in a loss of mass.
- D. invigorated: This means to give strength or energy to. This is the opposite of what happens after an accident and disuse.
- E. dwindled: While "dwindled" means to diminish in size, it is usually used for quantities (like money or supplies) rather than organic tissue. "Atrophied" is the precise technical term required for the GRE.

Final Completed Sentence
After the accident, the nerves to her arm were damaged and so the muscles atrophied through disuse.