**Core Concept**
The magnocellular and parvocellular neurons are types of neurons found in the hypothalamus, specifically in the supraoptic nucleus (SON) and the paraventricular nucleus (PVN). These neurons are responsible for producing and secreting various neurotransmitters and hormones, including vasopressin (ADH) and oxytocin. The projection of these neurons is crucial for maintaining homeostasis and regulating various physiological processes.

**Why the Correct Answer is Right**
The magnocellular neurons project to the posterior pituitary gland, where they release vasopressin (ADH) and oxytocin into the bloodstream. This release is triggered by the action of various stimuli, including changes in blood osmolality, blood pressure, and emotional states. The parvocellular neurons, on the other hand, project to the median eminence, where they release hormones that regulate various endocrine functions, including the release of adrenocorticotropic hormone (ACTH) and thyroid-stimulating hormone (TSH).

**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because the magnocellular neurons do not project to the cerebral cortex. The cerebral cortex receives input from various sensory and motor pathways, but it is not the primary target of the magnocellular neurons.

**Option B:** Incorrect because the parvocellular neurons do not project to the spinal cord. While the spinal cord does receive input from various neurons, the parvocellular neurons are primarily involved in regulating endocrine functions, not motor control.

**Option C:** Incorrect because the magnocellular and parvocellular neurons do not project to the cerebellum. The cerebellum is involved in motor coordination and learning, but it is not the primary target of these neurons.

**Option D:** Incorrect because the magnocellular and parvocellular neurons do not project to the hippocampus. The hippocampus is involved in memory formation and spatial navigation, but it is not the primary target of these neurons.

**Clinical Pearl / High-Yield Fact**
The magnocellular and parvocellular neurons play a crucial role in regulating various physiological processes, including fluid balance, blood pressure, and endocrine function. Dysfunction of these neurons can lead to various disorders, including diabetes insipidus and Cushing's disease.

**Correct Answer:** C. **Posterior Pituitary Gland**