Final answer:
Osteomalacia is the softening of the bones in adults due to calcium depletion.
Step-by-step explanation:
The best description of osteomalacia is option b) The softening of the bones in adults due to calcium depletion. Osteomalacia is a condition characterized by a deficiency of calcium and phosphorus in the diet or a combination of both, resulting in the demineralization of bones. Poor absorption of calcium from the intestine and decreased levels of activated vitamin D can contribute to this condition. Osteomalacia can also be caused by factors such as parathyroid deficiency and increased alkaline phosphatase activity.