Which of the following is true of interstitial, rather than appositional, chondrogenesis?

A) Chondroblasts differentiate within the chondrogenic layer of the perichondrium
B) Isogenous groups are formed by chondroblast mitosis
C) Interstitial chondrogenesis begins from undifferentiated cells
D) It results in an increase in the diameter or thickness of the cartilage
E) Spindle-shaped cells cluster together in the outer layer of the perichondrium