## Core Concept
The parathyroid glands are small endocrine glands located in the neck, playing a crucial role in regulating calcium levels in the blood. They produce **parathyroid hormone (PTH)**, which helps maintain calcium homeostasis by acting on bones, kidneys, and the intestine indirectly through effects on vitamin D metabolism.

## Why the Correct Answer is Right
The correct statement regarding the parathyroid glands involves their function and regulation. Typically, PTH release is stimulated by low serum calcium levels, and it acts to increase serum calcium. This involves PTH promoting the release of calcium from bones, increasing renal reabsorption of calcium, and enhancing the activation of vitamin D, which increases intestinal absorption of calcium.

## Why Each Wrong Option is Incorrect
- **Option A:** Without the specific details of option A, we can't directly address its inaccuracies. However, any statement contradicting the basic physiology of parathyroid glands, such as their role in calcium regulation or their anatomical location, would be incorrect.
- **Option B:** Similarly, without specifics, we assume any incorrect statement about parathyroid function, such as the regulation of PTH secretion or its effects on the body, would be wrong.
- **Option C:** This option's incorrectness would depend on it stating something false about parathyroid glands, such as their number, location, or the consequences of their dysfunction (e.g., hyperparathyroidism leading to hypercalcemia).
- **Option D:** As the correct answer is given as D, it implies D is a true statement about parathyroid glands.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **hyperparathyroidism** (an overproduction of PTH) can lead to **hypercalcemia** (elevated calcium levels), which presents with symptoms like "stones, bones, and abdominal moans" (renal stones, bone pain, and gastrointestinal symptoms). This condition highlights the importance of PTH in calcium homeostasis.

## Correct Answer: D.