**Core Concept**
The parathyroid glands are a group of small endocrine glands located in the neck, playing a crucial role in regulating calcium levels in the blood through the secretion of parathyroid hormone (PTH). There are four parathyroid glands in humans, with three usually located near the posterior aspect of the thyroid gland and one located near the inferior aspect.

**Why the Correct Answer is Right**
The correct number of parathyroid glands is essential for maintaining normal calcium homeostasis. Parathyroid hormone (PTH) is secreted by the parathyroid glands, which stimulates the release of calcium from bones, increases calcium absorption from the intestine, and decreases calcium excretion by the kidneys. The four parathyroid glands work in harmony to regulate calcium levels in the blood, ensuring proper muscle and nerve function.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it suggests a different number of parathyroid glands than the actual anatomical count.
**Option B:** This option is incorrect because it implies an abnormality in the number of parathyroid glands, which can lead to parathyroid hormone-related disorders.
**Option C:** This option is incorrect because it does not accurately represent the typical number of parathyroid glands found in humans.

**Clinical Pearl / High-Yield Fact**
A key clinical correlation is that parathyroid hormone (PTH) levels can be used to diagnose and monitor parathyroid disorders, such as primary hyperparathyroidism, which is characterized by an overproduction of PTH leading to hypercalcemia.

**Correct Answer: C. 4. There are 4 parathyroid glands in the human body.**