The correct answer is c) transport.
To understand why, let’s break down the primary functions of the kidneys. The kidneys are essential organs in the human body that perform several critical functions:
- Filtration: They filter out waste products and excess substances from the blood, producing urine.
- Reabsorption: They reabsorb necessary substances like water, glucose, and electrolytes back into the bloodstream to maintain balance.
- Secretion: They secrete certain substances such as ions and toxins into the urine for excretion.
However, transport is not a direct function of the kidneys. While the kidneys do play a role in regulating the transport of substances within the body through their filtration and reabsorption processes, the actual transport of substances is primarily managed by the circulatory system. In essence, the kidneys manage waste and fluid balance, but they do not transport substances throughout the body themselves.