Question

in bone, the calcium phosphate forms crystals of
calcium carbonate
calcitriol
osteoid matrix
proteolytic enzymes
hydroxyapatite

Explanation:

In bone, calcium phosphate combines with hydroxide ions to form hydroxyapatite crystals which give bone its hardness and rigidity. Calcium carbonate is a different compound, calcitriol is a vitamin - D metabolite, osteoid matrix is the non - mineral part of bone, and proteolytic enzymes are involved in protein breakdown and not related to bone calcium phosphate crystals.

Answer:

E. hydroxyapatite