The correct option is
D Interferons
The above given picture is of viruses. They are obligate intracellular parasites, live inside cells and use the cell's machinery for the synthesis and multiplication of their own proteins. Cytokine barriers are a type of innate immunity that include the chemicals called interferons released by the virus infected cells, in order to prevent the spread of the virus to other cells. Interferons interfere with the multiplication of viruses. They act in three ways mainly.
They signal the neighbouring cells to destroy RNA and reduce protein synthesis.
They signal the neighbouring infected cells to undergo apoptosis (programmed cell death). So that virus cannot attack them.
They activate other immune cells (like natural killer cells,macrophages) so that these cells can attack viruses.
Therefore, cytokines are the specific barriers for the viruses. So the answer is option (d).
Physical barriers mainly include the skin and mucous membranes and prevent the human body against a variety of microorganisms. They are present in an organism by birth itself. They are not acting as a specific barrier against viruses.
Physiological barriers mainly include body fluids that prevent microbial growth such as acid in the stomach. Acidic pH (2-3) is not suitable for bacterial growth. This provides protection against a variety of microorganisms but not a specific barrier against viruses.
Cellular barriers include different types of WBCs which provide protection against a variety of microorganisms. Basophils are a type of white blood cells associated with inflammatory reactions (swelling and redness in the affected areas).