Which of the following statements is true of cartilage and bone development?
a. some cartilage becomes bone through ossification during childhood development.
b. cartilage produces white blood cells, which are necessary for immune system health.
c. cartilage is in the nose and ears, and cartilage can't become bone.
d. cartilage is the primary material responsible for moving sharks' bones.

A. some cartilage becomes bone through ossification during childhood development.

Explanation:

Ossification is a process of bone remolding, this starts from fetal stage and continues up to adolescence. The cartilage cells are replaced by the osteoblasts for the formation of bones in the cluster form.

option: A

Explanation:

The ossification process allows the formation of new bones in the body. The process begins from the fetal stage and it continues till adult age. The osteoblasts cell replaces the dead cartilagenous cells.

The hematopoietic stem cell synthesizes WBCs not cartilage. The cartilage can easily be transformed to a bone.The cartilage is not primary material for moving shark bones.  As the baby grows the small bones fuses with each other thus forming large bones. So the option A is correct.