Correctly order the following key steps in the process of endochondral ossification. 1. Chondrocytes die. 2. Osteoblasts build the bone collar on the external surface of the bone. 3. Perichondrium is invaded by blood vessels. 4. In the primary ossification center, osteoblasts replace calcified cartilage with early spongy bone. 5. Perichondrial cells differentiate into osteogenic cells then into osteoblasts.

Explanation:

cuz they cant breath

explanation:

the relative atomic mass of an element is the mass of one atom of that element, relative to 1/12th of the mass of a  1212c atom. to convert to an absolute mass in kg, it is necessary to multiply by  1.661×10−271.661×10−27.

the relative atomic mass is roughly equal to the number of neutrons, plus the number of protons, in the nucleus of the atom.

for elements with more than one stable isotope (different types of nucleus with different numbers of neutrons but the same number of protons), the quoted mass is usually the average mass, weighted by the relative abundance of the different isotopes.