question: what are regulated by feedback mechanisms?
choices.text: trucks and cars h2o intake chemical messengers some prokaryotes antigens that cause allergy skin cells density prokaryotic cells
choices.label: A B C D E F G H
fact2: Hormones act as chemical messengers.
combinedfact: most chemical messengers are regulated by feedback mechanisms
formatted_question: what are regulated by feedback mechanisms? (A) trucks and cars (B) h2o intake (C) chemical messengers (D) some prokaryotes (E) antigens that cause allergy (F) skin cells (G) density (H) prokaryotic cells