What is the harder outer covering of a crab called?

The fauces connects which of th following structures to the oropharynx

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

Diffusion and osmosis are forms of passive transport