**Core Concept**
Myasthenia gravis is an autoimmune disease characterized by the production of antibodies against components of the neuromuscular junction, leading to muscle weakness and fatigue. This disease results from a defect in the transmission of nerve impulses to muscles.

**Why the Correct Answer is Right**
In Myasthenia gravis, the primary autoantibody targets are the acetylcholine receptors (AChR) at the postsynaptic muscle endplate. These antibodies cause a decrease in the number of functional AChR, impairing the binding of acetylcholine to the receptors and subsequent depolarization of the muscle membrane. This leads to a reduction in the number of muscle action potentials, resulting in muscle weakness. Some patients may also have antibodies against the muscle-specific kinase (MuSK) or the low-density lipoprotein receptor-related protein 4 (LRP4), but AChR antibodies are the most common.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because, although some patients with Myasthenia gravis may have antibodies against the muscle-specific kinase (MuSK), this is not the primary target in most cases.
**Option B:** This option is incorrect because the target of the antibodies in Myasthenia gravis is not the acetylcholine itself, but rather the receptors for acetylcholine on the muscle endplate.
**Option C:** This option is incorrect because the low-density lipoprotein receptor-related protein 4 (LRP4) is a target in some cases of Myasthenia gravis, but it is not the most common target.

**Clinical Pearl / High-Yield Fact**
A key clinical feature of Myasthenia gravis is the improvement in muscle strength following administration of anticholinesterase inhibitors, such as pyridostigmine, which increases the concentration of acetylcholine available for binding to the remaining functional AChR.

**Correct Answer: C. Acetylcholine receptors (AChR)**