Correctly order the following steps of bone growth in length by placing a 1 by the first step, a 2 by the second step, and so on.
Calcified cartilage is replaced with bone in the zone of ossification.
Chondrocytes in the zone of proliferation divide by mitosis.
Chondrocytes enter the zone of calcification and die as their matrix calcifies.
Chondrocytes enlarge and cease dividing.