What is menstruation, and how is the process triggered during each "monthly" cycle?

Regarding most of the narrator’s story, which word best describes the tone?

8) animals respond in various ways to stimuli detected through their senses. some of these responses are stimulated by the presence of danger. which of these animal responses is the best example of a response to an immediate threat? a) a rooster crows every morning at the first sign of light. b) as something approaches an octopus, it shoots a cloud of ink. c) from late fall until spring, bears hibernate to preserve energy. d) a dog is getting hot in the sunlight, so he moves to a shaded area.

Which macromolecule catalyzes chemical reactions this be considered enzyme chemical reactions thus he considering enzymes