What are the signs of dehydration?

The signs of dehydration prominently include dry mouth, thirst, decreased urine output, and confusion. These symptoms are classic indicators that the body is not receiving adequate fluids, or is losing more fluids than it can replenish.

Dry mouth and thirst are the body's immediate responses to a lack of hydration, signaling the need for fluid intake. Decreased urine output occurs because the kidneys conserve water to maintain essential bodily functions, which also enhances concentration of the urine. Confusion may arise as dehydration affects neural activity and cognitive functions, particularly in more severe cases.

The other options do not specifically indicate dehydration. High fever and fatigue might point to an illness or infection but are not direct indicators of dehydration alone. Nausea and vomiting can contribute to dehydration but are also symptoms of various other conditions. Swelling in the legs is typically associated with fluid retention or other issues such as heart failure and does not directly reflect a dehydrated state. Thus, option B accurately encapsulates the distinctive symptoms associated with dehydration.