Homozygotes with two sickle-cell alleles are selected against because of mortality. However, heterozygotes for sickle-cell allele experience little effects of sickle allele and are more likely to survive malaria. The net effect of this exposure produced evolutionary change in areas where malaria is endemic by .

causing sickle-cell allele
distortion of red blood cells
increasing sickle-cell allele frequency
increasing the number of infected mosquitoes

increasing sickle-cell allele frequency

Explanation:

Sickle cell anemia is the most common inherited blood disorder in the United States. In the United States, approximately 100,000 people have SCD. SCD occurs in about 1 of every 16,300 Hispanic-American births. Approximately 1 in 13 black or African Americans has sickle cell trait.

Sickle cell disease (SCD) affects millions of people throughout the world and is particularly common among those whose ancestors came from sub-Saharan Africa; Spanish-speaking regions in the Western Hemisphere (South America, the Caribbean, and Central America); Saudi Arabia; India; and Mediterranean countries such as Turkey, Greece, and Italy.

Option-(C):

Explanation:

after receiving a stimus, the sensory receptors send(s) signals to the appropriate area of the body.  

the must be sensory neurons.  

hope its .