As a person exercises, carbon dioxide (co2) levels in the blood increase. This causes the nervous system to signal which of these systems to respond?

Wats iqpow pls write 20 words for an answer

Based on the narrator's comments about living with the widow douglas, the reader can infer that a) the narrator doesn't care much for civilization and its strict rules. b) the narrator admires and wants to become more civilized and refined. c) the narrator is extremely religious and of high moral standing. d) the narrator desires to become a productive member of society.

Which of the following always exist between two objects having mass ● elastic force ● contact force ●gravitational force ●magnetic force