What is the primary function of excretion?

The primary function of excretion is to remove metabolic waste products from the body. This process is essential for maintaining homeostasis, as the accumulation of waste products can be toxic and affect the overall functioning of the organism. Excretion involves various systems within the body, mainly the urinary system, which filters blood to remove waste products such as urea, creatinine, and other metabolites that arise from cellular processes. By eliminating these substances, the body ensures that its internal environment remains stable and conducive to cellular activities.

In contrast, the other options do not pertain directly to the role of excretion. Absorbing nutrients is tied to digestion, not excretion; regulating body temperature involves thermoregulation mechanisms separate from waste removal; and facilitating digestion pertains primarily to the digestive system's role in breaking down food and absorbing nutrients, rather than expelling waste. Thus, option B accurately captures the essence of excretion's vital role in organismal health and homeostasis.