Final answer:
Endochondral ossification replaces hyaline cartilage to form long bones, while intramembranous ossification replaces undifferentiated connective tissue to develop flat bones like those of the skull.
Step-by-step explanation:
The correct answer is A. Endochondral ossification replaces hyaline cartilage, whereas intramembranous ossification replaces undifferentiated connective tissue. Endochondral ossification is essential for the formation of long bones and is a process where the bone forms by gradually replacing hyaline cartilage. This cartilage serves as a template for bone construction but is not converted into bone itself. In contrast, intramembranous ossification is involved in the development of flat bones of the skull, where bone develops directly from sheets of mesenchymal connective tissue without a cartilage template.