Nthe semi arid regions of china, the country's inhabitants have practiced water harvesting for generations. water harvesting is the process of collecting rainfall and/or runoff for later use. how does this water conservation method the environment?
a) water harvesting causes drought-like conditions the rest of the year.
b) keeping the water for later use leads to over farming and land degredation.
c) water harvesting causes the area to become uninhabitable the rest of the year.
d) by collecting runoff during the rainy season much of the land degredation caused by water erosion is prevented.

we solve the problem using the hardy-wineberg equation.

let us start with the homozygous recessive proportion of individuals with sickle cell anaemia,

we have the proportion as q² = 0.25.

∴ q = 0.5 (frequency of hbs in population)

further,

solving for the frequency of normal cell by using the fact that,

p + q = 1

∴ p = 1 - 0.5 = 1 - 0.5 = 0.5

now we can calculate 2pq in p² + 2pq + q², which is the frequency for heterozygous carriers of sickle cell anaemia,

∴ 2pq = 2 x 0.5 x 0.5 = 0.5

and the homozygous normal cell individuals proportion is given by the expression,

∴ p² = 0.5² = 0.25

hence, the carriers for sickle cell anaemia are in proportion, 0.5, or 50%.