Answer:
The correct answer is option B. has a defective allele and normal phenotype.
Explanation:
Genetic carrier or the hereditary carrier is an organism or a person that has a recessive allele for a particular trait or character (generally mutation) but does not exhibit the trait or any character related to the trait.
The carriers are normal in the sex-linked characters in comparison to the autosomal traits. Females are generally the carrier for sex-linked characters and carry the allele to the next generation.
Thus, the correct answer is option B. has a defective allele and normal.
Some ways in which communicable diseases spread are by: physical contact with an infected person, such as through touch (staphylococcus), sexual intercourse (gonorrhea, HIV), fecal/oral transmission (hepatitis A), or droplets (influenza, TB) travel through the air, such as tuberculosis or measles.
Answer:
Red allele frequency will be highest in population II
Population III can undergo bottleneck effect
The frequency of the brown allele will least likely be altered in the population I
Explanation:
Population I -
Total population - 
Brown birds - 
Red birds - 
Population II
Total population - 
Brown birds - 
Red birds - 
Population III
Total population - 
Brown birds - 
Red birds - 
Frequency of red birds in population I

Frequency of red birds in population II

Frequency of red birds in population III

Red allele frequency will be highest in population II and it will be equal to
as compared to
in case of population I and III
Population III can undergo bottleneck effect because of smaller population size
The frequency of the brown allele will least likely be altered in the population that has highest brown individual , i.e population I