複選題19. Which of the following is true about nucleosomes? (A) Nucleosomes are composed of DNA wound around an octameric complex of histone molecules. (B) Nucleosomes contain four major types of histones: H1, H2, H3, and H4. (C) Nucleosomes are the most abundant chromatin proteins. (D) Nonhistone proteins are necessary for the reconstitution of the nucleosome core. (E) All are true.