How is a metamorphic rock formed?

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

What is the name of the type of cell division that occurs in the prokaryotic cell cycle

Why are scientists concerned about the depletion of the ozone levels in the stratosphere?