The correct answer is lack of calcium.
Explanation:
Osteoporosis is a disease in which the bones become fragile and can break easily.
It is very likely to appear in a person over 50 years old, especially if she is a woman.
This disease is caused by a deficit of calcium in the bones, since calcium is essential for bones to be healthy and strong.
To avoid this, it is recommended to consume foods that contain a lot of calcium and vitamin D.
Given this information, we can say that the correct answer is lack of calcium.