Question

interferon is a group of proteins produced by cells in response to the presence of
chemical irritants.
bacterial cells.
malarial parasites.
viruses.

Explanation:

Interferons are proteins that play a crucial role in the body's immune response. They are specifically produced by cells when the body detects the presence of viruses. Chemical irritants, bacterial cells, and malarial parasites do not trigger the production of interferons. When a virus infects a cell, the infected cell releases interferons. These interferons then signal neighboring cells to prepare for a potential viral attack by up - regulating antiviral genes. This helps in limiting the spread of the virus within the body.

Answer:

viruses.