Explanation:

Here’s the thing—when you hear “soft bones” in adults, think osteomalacia. That’s the medical term for bone softening from vitamin D deficiency, lack of sunlight, or sometimes gut or kidney issues.

- Option 1: Osteopenia

This means lower-than-normal bone density, but the bones aren’t soft, just less dense. It’s a midway point between healthy bones and osteoporosis.

- Option 2: Osteomyelitis

This isn’t about soft or weak bones at all. It’s an infection, usually bacterial, inside the bone. Totally different story.

- Option 3: Osteomalacia

Here’s your answer. This is the adult disease where bones get soft because of low vitamin D or other absorption problems. Not brittle, not less dense—just oddly and dangerously soft.

- Option 4: Osteoporosis

This condition is all about bones becoming brittle and prone to breaking, not soft. It’s due to loss of bone mass, not lack of vitamin D per se.