During which period did manual fist appear a. pleistocene b. carboniferous c. cretaceous d. jurassic

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

If animal agriculture was eliminated, how much grain would become available for human consumption?

Nh3 +02-no + h20 is unbalanced what is the balanced equation