What are the two main functions of the kidneys?

The primary functions of the kidneys include filtering blood and regulating fluid balance, making option B the correct choice.

The kidneys are essential organs within the urinary system responsible for eliminating waste products from the blood and ensuring that the body's fluid levels remain balanced. They filter out toxins, excess salts, and water, which are then excreted as urine. This filtration process is crucial for maintaining homeostasis, which is the stable internal environment necessary for the proper functioning of the body.

Additionally, the kidneys play a significant role in regulating blood volume and, consequently, blood pressure. By adjusting the volume of urine produced based on the body's hydration status, the kidneys help keep the fluid balance in check, preventing both dehydration and fluid overload.

While the other options mention functions that are important in their own right, they do not accurately describe the primary functions of the kidneys. For instance, digestion and nutrient absorption are functions of the gastrointestinal system rather than the kidneys. Similarly, temperature regulation and hormone production, while relevant to bodily functions, do not encompass the core responsibilities of the kidneys, which focus on blood filtration and fluid regulation.