I believe it's B. Apologies if I'm wrong.
Answer:Valves stop blood flowing backwards
Explanation: Valve are flags of tissue that control the direction of the blood in our heart.,it prevent the backwards flow of blood. valves regulate blood from flowing back into the atria.The right and left atrio-ventricular valves prevent blood from flowing backwards into atria. When the ventricle is full,the valve prevent backwards flow of blood.
The DNA has to replicate before mitosis to keep the number of chromosomes consistent. Hope this helps.
Answer:
Photosynthesis a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's metabolic activities
they need sun water and CO2
Explanation:
