Sickle cell anemia is an inherited form of anemia - a condition in which there aren't enough healthy red blood cells to carry adequate oxygen throughout your body. Normally, your red blood cells are flexible and round, moving easily through your blood vessels. In sickle cell anemia, the red blood cells become rigid and sticky and are shaped like
sickles or crescent moons. These irregularly shaped cells can get stuck in small blood vessels. How does sickle cell anemia affect the blood flow in a human?

RBCs are round red blood cells that easily move through blood vessels and carry oxygen with them to provide cells oxygen. In sickle cell anemia, the shape of the red blood cells is like sickles or crescent moons.

These cells occur due to mutation on the gene that produces this protein which results in rigid, sticky cells that can get stuck in small blood vessels and blocks the flow of blood, oxygen to parts of the body.

the correct answer is - d. china has a large and growing population.

the fact that china has a large (the biggest) population, and it is still growing, doesn't hinder the agriculture production in the country. in fact, it can for increased production in the agriculture, since there's more labor force, as well the sheer mass of people produces lots of scientists that come up with new inventions as to how to improve this sector. nice example is the inner mongolia region in china, in general dominated by the gobi desert, but few scientist came up with a nice idea as to how to make the region productive by using plants that are very resistant to droughts, so lots of people have been employed, and the region is becoming greener and greener each year, and the production of food in this region is also increasing.

d. organisms have cells with different shapes and functions.