Which of the following best defines perspiration?

Perspiration is best defined as the excretion of sweat. This process is a crucial function of the body for regulating temperature and eliminating certain waste products. When the body overheats, the sweat glands produce sweat, which is primarily composed of water, salts, and some metabolic waste. As sweat evaporates from the surface of the skin, it cools the body, helping to maintain a stable internal temperature. This physiological mechanism plays a vital role in thermoregulation and can also aid in hydration levels, although the primary purpose of perspiration is to cool the body.

The other choices relate to different bodily functions: breathing involves the exchange of gases, blood flow refers to the circulation of blood throughout the body, and digestion pertains to the breakdown of food into nutrients. Each of these functions is significant in its context, but they do not pertain directly to the definition of perspiration as the process of excreting sweat.