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.
Explanation:
Ice actually has a very different structure than liquid water, in that the molecules align themselves in a regular lattice rather than more randomly as in the liquid form. It happens that the lattice arrangement allows water molecules to be more spread out than in a liquid, and, thus, ice is less dense than water.
<h2>C) option is correct </h2>
Explanation:
Natural selection as proposed by Darwin is a selection pressure which operates in a population and allow the best fitted genotype to survive in changing environmental conditions and eliminate the other genotype which are not fit
Causes of natural selection include: Genetic drift, mutation(changes allelic frequency) and sexual selection
In the given example, condition necessary for natural selection to occur on the mouse population is traits that affect the survival of the mice vary among individual mice, in this condition superior genotype will get the opportunity to reproduce and inferior genotype does not get opportunity to reproduce thus their genotype in population does not increase rapidly and hence they become eliminated leading to genetic drift
