What is an epitope? the complementarity-determining regions of lymphocyte receptors the portion of an antigen that binds covalently to an antibody the part of an antibody that determines its isotype a small portion of an antigen that binds specifically to lymphocyte receptors?

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