In bronchopulmonary dysplasia, the lungs of newborns become inflamed and scarred. Most infants recover, but some die. An experimental treatment cultures stem cells from a newborn's umbilical cord. The stem cells, in a lab dish, give rise to type II cells, which in turn give rise to more type I cells. In this treatment
A. the type I cells secrete surfactant and the type II cells form the respiratory membrane.
B. the type II cells secrete surfactant and the type I cells form the respiratory membrane.
C. the stem cells enable the baby to grow new lungs.
D. the stem cells directly replace alveoli.
E. both type I and type II cells produce surfactant.