Answer:not sure but i think b!
Explanation:
<span>The Answer is Interphase</span>
Veins contain valves that ensure blood flows in only one direction. Valves also help blood travel back to the heart against the force of gravity.
Hope this helps.....
The average atomic mass of an element<span> is the sum of the </span>masses of its isotopes, each multiplied by its natural abundance (the decimal associated with percent of atoms<span> of that </span>element<span> that are of a given isotope).</span>
