Please help its a very difficult question

There are six elements that make up most of the human body. which of the following is not one of these six elements?

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

Nerve cells are specialized to respond to stimulitrue or false?