The respiratory system depends on the nervous system for signals to
a. coordinate the muscles that control breathing.
b. exchange gases with the circulatory system.
c. enhance the amount of available oxygen in the lungs.
d. release enzymes to increase the exchange of gase

Johnny rode his bike to a friend's house 4 blocks down the street in his neighborhood. he immediately rode back home once he realized his friend was not able to play. what was his displacement for the total bike ride? how did you determine this? what could we use as a reference point to determine he was in motion during his bike ride? why can you use it as a reference point