A hypothesis that describe how you think the rock model with stones will break down.

it would be c. xylem.

sex cells are usually half's then they find another half and make a fertilize egg

multiple allele inheritance is traits controlled by more than 2 alleles (ex: pigeons having 3 alleles of one gene govern their feather color).   so the answer is a.

instead of copying and pasting things off of tests or work done on computer which im sure you did, try and read over the question carefully