What is the metabolic abnormality that underlies the characteristic symptoms of diabetes mellitus?
A. A failure of the kidney tubules to reabsorb glucose from the urine
B. A failure of the villi of the intestine to absorb glucose from food
C. The body can't switch from glucose metabolism to fat metabolism between meals.
D. The body's cells can't retain glucose absorbed from the blood.
E. The body's cells can't absorb enough glucose from the blood.