According to the passage, which of the following is required for lactation

A．The fetus grows at the expense of the mother.
B．Good nutrition is necessary throughout pregnancy.
C．The most important changes occur in early pregnancy.
D．The mother's nourishment is more important than the baby's.

A．how the human fetus develops
B．the benefits of breastfeeding
C．methods of achieving proper maternal nutrition
D．the effect of maternal nutrition on the fetus