Final answer:
The brain receives the second highest amount of metabolic energy after the liver and spleen, and the muscles lose the most energy due to high cellular respiration and heat maintenance needs.
Step-by-step explanation:
The question pertains to the energy distribution and utilization within different organs of the body concerning their metabolic functions. When it comes to energy distribution, the liver and spleen receive the largest fraction of energy in the basal metabolic rate, while the brain comes next in line. Approximately 75% of food calories are used to sustain basal life functions including the basal metabolic rate. Concerning energy loss, the most energy is spent on cellular respiration and maintaining internal heat, especially in organs with high metabolic activities such as the muscles.
Considering this information, the answer to the question is that the brain receives the second highest amount of energy and the muscles lose the most energy for cellular respiration and internal heat maintenance. Hence the correct answer to the fill-in-the-blank question would be A) Brain, Muscles.