**Core Concept**
Myasthenia gravis is an autoimmune disease characterized by the production of antibodies against acetylcholine receptors (AChR) at the neuromuscular junction, leading to muscle weakness and fatigue. Certain medications can exacerbate this condition by either increasing the autoimmune response or interfering with neuromuscular transmission.

**Why the Correct Answer is Right**
The correct answer is likely a drug that does not exacerbate myasthenia gravis. Drugs that worsen myasthenia gravis typically act by increasing the autoimmune response, blocking acetylcholine receptors, or inhibiting acetylcholinesterase, the enzyme responsible for breaking down acetylcholine. For example, aminoglycoside antibiotics can block acetylcholine receptors, while d-penicillamine can increase the production of antibodies against AChR.

**Why Each Wrong Option is Incorrect**
**Option A:** Aminoglycoside antibiotics, such as gentamicin, can block acetylcholine receptors and worsen myasthenia gravis.
**Option B:** D-penicillamine, a chelating agent used to treat Wilson's disease, can increase the production of antibodies against AChR and exacerbate myasthenia gravis.
**Option C:** Procainamide, an antiarrhythmic medication, can also exacerbate myasthenia gravis by increasing the autoimmune response.

**Clinical Pearl / High-Yield Fact**
It's essential to recognize that medications can have a significant impact on patients with myasthenia gravis, and clinicians should carefully weigh the benefits and risks of each medication before prescribing.

**Correct Answer: D.**