I think it's D) atmospheric carbon dioxide.
When water molecules
diffuse through a cell membrane this process is called the osmosis. Water
molecules are extremely small and because of this they can slip freely through
the gaps between the phospholipids in the cell membrane. And as a result, water
molecules can constantly move back and forth though the cell <span>
membrane. This movement of water has a very important
function and that is it enables cells to absorb water. </span>
Now for a movement of
water molecules to happen, there should be a concentration gradient in the surrounding.
That is, the amount of water in one side must be different on the other side.
<span>For water to diffuse
INTO the cell, the amount of water outside the cell membrane should be larger
than the amount of water inside the side.</span>
A dihybrid cross is defined as a breeding experiment involving parental generation chromosomes that have two contrasting traits. The individual organisms involved in this can be either homozygous or heterozygous.
This kind of cross pollination experiments led to the development of George Handel's Law of Independent Assortment.
Hope it helps.
