The correct option is C urea
Glucose is unavailable during prolonged fasting. Body starts utilizing accumulated fat to meet the energy requirement. During the process of fat metabolism, it produces ketones which ultimately increases the blood ketone level. Generally, they are reabsorbed by the kidney during blood filtration. However, since the levels of ketones in the blood are higher than the reabsorption capacity of the kidneys during prolonged fasting, these ketones spill over into the urine. Hence, high level of ketones and low level of urea will be found in urine during prolonged fasting.