Correct answer: C) Concentration gradient
The process of movement of a particle in a solution from the region of higher concentration to the region of lower concentration across a membrane is called as concentration gradient.
For example: If we drop a few drop of dye in a glass of water, it will diffuse along a concentration gradient, i.e, the region where dye is found in highest concentration to the region where it is in lower concentration.
It will occur until the concentration of dye become uniform in all the direction in the glass of water.
Answer:
There will be 12 chromosomes
Explanation:
We have given that The epithelial cells in the skin of an animal have 24 chromosomes
We have to find the number of chromosomes present in the gametes of this animal
We know that number of chromosomes present in the gametes is given by
So number of chromosomes in gametes 
A tolerance range is an environment where something can survive in. But if their is to much of one factor or to little this can effect the tolerance range.
The difference between an artery and a vein is that arteries are larger, more muscular and more elastic than veins; they carry blood that is under pressure from having been pumped out of the heart; veins are under much less pressure, so they are not as strong
