Answer: Option A.
The hypothalamus is the brain structure responsiblre for regulating thirst, hunger, temperature and sexual behaviour.
Explanation:
Hypothalamus is a part of brain structures located at the floor of the third ventricle below the thalamus and its control the autonomic system.
It controls hunger, thirst, temperature, fatigue, sleep and sexual behaviour . Hypothalamus secretes the anti diuretic hormones which increases the level of water absorbed into the blood by the kidneys and corticotropin releasing hormone which regulate immune system.
The evolutionary effects of the genetic drift are the greatest when the population is small.
In small populations, genetic drift can significantly change the frequencies of the alleles and affect the genetic structure of the population. In big populations, the effects of the genetic drift are small and insignificant.
Here, given-
homozygous alleles 'a' have a frequency of 0.3.
Also the alleles are in equilibrium in a Hardy-Weinberg population. The frequency of individuals that are homozygous for this allele are= 0.49.
The Hardy-Weinberg equilibrium can be defined as the principle which states that the variation in the genetic makeup of a population remains constant and unchanged till there are no external interferences, influencing the population.
Calculation-
Then to find the frequency of the individuals homozygous for this allele the following formula needs to be used-
Thus, the individuals homozygous for the allele can be calculated by 
Learn more about the Hardy-Weinberg equilibrium here-
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The answer would be A. thick filaments!
Answer:
Point mutations are a broad category of mutations that describe a change in a single nucleotide of DNA, such as a substitution for another nucleotide, deletion of a nucleotide, or insertion of a single nucleotide into the DNA, resulting in DNA that differs from the normal or wild type gene...
or you can say:
Point mutations are a large category of mutations that describe a change in single nucleotide of DNA, such that that nucleotide is switched for another nucleotide, or that nucleotide is deleted, or a single nucleotide is inserted into the DNA that causes that DNA to be different from the normal or wild type gene ...
