Given a scientific question, generate a correct answer to it.

[Q]: Strong, stable bonds between carbon atoms produce complex molecules containing chains, branches, and rings; the chemistry of these compounds is called what?
[A]: organic chemistry

[Q]: What type of fibers are made mostly of protein in living things?
[A]: muscle fibers

[Q]: Rh antibodies can prove dangerous if they cross what barrier in pregnancy?
[A]:
placental