Answer:
Osteoid
Explanation:
The earliest form of spongy bone in a developing long bone is termed as Osteoid.
Osteoid is defined as the the unmineralized, matrix material that is made up of a fibrous protein, collagen, and mucopolysaccharide and forms prior to the maturation of bone tissue.
Osteoblasts, the process of formation of bones takes place when inorganic salts starts depositing over osteoid to form the hardened material.
Hence, the correct answer is "Osteoid".
