It Is Believed That a Virus Contracted by a Pregnant

It is believed that a virus contracted by a pregnant woman might increase the incidence of schizophrenia in her child because:

A) a mother's fever can adversely affect fetal brain development.
B) increases in the resulting stress hormones in the mother affect fetal hormone levels.
C) viruses are able to cross the placenta and affect the fetus directly.
D) viral infections will harm the umbilical cord hampering the delivery of nutrients to the fetus.