C. why an understanding of physical development is essential. D. the role that health, diet, and safety play in physical maturation. E. all of the above 3. Infants are expected to support their heads before they can twist their trunk to roll over. B. cephalocaudal progression D. proximodistal progression 4.
Muscle fibers change in several ways during development.
A. length C. number B. thickness D. water content 5. A. medulla C. axon B. neuron D. cortex E. myelin 7. E. all of the above 8. B. Girls are two years ahead of boys in physical development during puberty. D. Reproductive fertility cannot be precisely tied to visible physical developments such as menarche or first ejaculation.