Your Friend Ellie Is Pregnant

Your friend Ellie is pregnant. She tells you that her mother, a microbiologist, has warned her not to clean out the cat's litter box while she is pregnant in case she contracts a disease called toxoplasmosis, which can affect her fetus. She says her mom told her toxoplasmosis is caused by a parasite called Toxoplasma gondii, that may be found in the feces of infected cats and also in raw meat. Your friend's mom tells her that when a person has not had a particular disease, they are not immune to the pathogen that causes the disease, and lack antibodies against that microbe. Your friend has never had toxoplasmosis but she doesn't quite understand why this, and the fact that she doesn't have antibodies to T. gondii, is important. You help her understand some facts about her adaptive immune system.
-A fetus is protected by maternal antibodies that cross the placenta. You explain to Ellie that the fetus

A) is protected by both maternal IgG and maternal IgM, because these can easily cross the placenta.
B) is protected by maternal IgM but not by maternal IgG, because IgM can cross the placenta but IgG cannot because it is a pentamer.
C) will make large amounts of its own IgG and IgM immediately if the mother contracts some type of pathogen.
D) is protected by maternal IgG but not by maternal IgM-IgG can cross the placenta but IgM cannot because it is a pentamer.
E) will make its own IgG if the mother contracts any type of pathogen; it cannot make IgM because this is a pentamer.