Answer: All the statements of the question are correct.
Sickle cell disease is an autosomal recessive disorder that is characterized by formation of defective hemoglobin protein, which results in sickle shaped RBC ( red blood cell).
This disease is caused by mutation in the gene that is responsible for the protein hemoglobin ( which transport oxygen throughout body).
It is inherited by the offspring when both the mutated copy of genes ( one from each parent) are passed to him.
Carriers of the disease exhibit increased resistance to malarial parasites by controlling the level of free haem in the blood ( through enzyme heme oxygenase that produces a toxic carbon monoxide gas). The resistance thus developed, is a mutation.
Therefore, all the statements in the given question are correct.
Classification is subject to change because science is an evolving subject. New things are discovered every year and thus changing the way we understand the world around us.
The correct answer is (c) discover antigens in body fluids.
B lymphocytes act as antigen presenting cells that recognizes and displays the antigen to the white blood cells. These cells process the antigens that are present in body fluids. Professional antigen presenting cells includes B-lymphocytes, macrophages, dendritic cells, etc.
