Why are GMO foods controversial?

What type of specimens where you able to see under each of the microscopes in the microscope activity

Cells destroy body cells infected by a virus or bacteria.

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