In What Way Are Monotremes Similar to More Ancestral Chordate

In what way are monotremes similar to more ancestral chordate lineages, as opposed to more recently evolved mammals?

A) Monotremes perform little parental care; other mammals use lactation to feed offspring.
B) Monotremes exchange gases through their skin; other mammals use lungs.
C) Monotremes lay eggs; other mammals bear live young.
D) Monotremes do not have jaws; other mammals do.
E) Monotremes perform external fertilization; other mammals perform internal fertilization.