**Core Concept**
Baroreceptors are specialized sensory receptors located in the walls of blood vessels, particularly in the carotid sinus and aortic arch. They play a crucial role in regulating blood pressure (BP) by detecting changes in arterial pressure and sending signals to the brain to adjust heart rate, cardiac output, and vascular tone accordingly.

**Why the Correct Answer is Right**
Baroreceptors are sensitive to changes in blood pressure within a specific range. When blood pressure increases, baroreceptors are stretched, and they send signals to the brain to activate the parasympathetic nervous system, which slows heart rate and reduces cardiac output. Conversely, when blood pressure decreases, baroreceptors are less stretched, and they send signals to the brain to activate the sympathetic nervous system, which increases heart rate and cardiac output. This reflex helps to maintain blood pressure within a narrow range, typically between 60-140 mmHg systolic and 40-90 mmHg diastolic.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because baroreceptors are not responsible for regulating blood pressure at very low pressures, such as those seen in severe hypotension. In such cases, other mechanisms, such as the renin-angiotensin-aldosterone system, come into play.
**Option B:** This option is incorrect because baroreceptors are not primarily responsible for regulating blood pressure during exercise or physical activity. In these situations, the sympathetic nervous system is activated, and baroreceptors play a secondary role in modulating blood pressure.
**Option C:** This option is incorrect because baroreceptors are not sensitive to changes in blood pressure below a certain threshold, typically around 40-60 mmHg systolic. Below this threshold, other mechanisms, such as the baroreflex, are activated to maintain blood pressure.

**Clinical Pearl / High-Yield Fact**
Baroreceptors are often referred to as the "volume reflex" because they help to regulate blood volume by detecting changes in blood pressure and sending signals to the brain to adjust cardiac output and vascular tone accordingly. This is an important concept to remember when evaluating patients with volume depletion or overload.

**Correct Answer: C. 60-140/40-90 mmHg**