Pick the right answer for me

What is the chance of two parents with blood types ab and o producing an offspring with blood type o a.0% b.25% c.75% d.50%

How can you keep track of variables in a science experiment?

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