**Core Concept**
Muscle weakness can be caused by disorders affecting the neuromuscular junction, such as myasthenia gravis. Neostigmine is an anticholinesterase inhibitor that increases the concentration of acetylcholine at the neuromuscular junction, thereby improving muscle strength.

**Why the Correct Answer is Right**
Neostigmine works by inhibiting the enzyme acetylcholinesterase, which breaks down acetylcholine. By preventing the breakdown of acetylcholine, neostigmine increases the amount of acetylcholine available to bind to nicotinic receptors on muscle cells, leading to increased muscle contraction and strength. In patients with myasthenia gravis, the immune system mistakenly attacks and destroys these nicotinic receptors, reducing muscle strength. By increasing acetylcholine levels, neostigmine helps to compensate for the reduced number of receptors.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because it does not provide a clear mechanism for how neostigmine reverses muscle weakness.
* **Option B:** This option is incorrect because it suggests that neostigmine works by increasing the production of acetylcholine, rather than by preventing its breakdown.
* **Option C:** This option is incorrect because it implies that neostigmine works by affecting the muscle cells themselves, rather than by improving neurotransmission at the neuromuscular junction.

**Clinical Pearl / High-Yield Fact**
Neostigmine is a classic example of an anticholinesterase inhibitor, and its use in patients with myasthenia gravis is a key part of their management. It's essential to remember that neostigmine works by increasing acetylcholine levels, not by altering the number of nicotinic receptors.

**Correct Answer:** C.