Life is amazing.. live it to the fullest

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

Which best describes carbon dioxide’s path out of the body

What are antigens and antibodies? how are they involved in the body’s response to incompatible blood?