Final answer:
Interferons are cytokines released (Option B) by virally infected cells to alert surrounding cells to produce antiviral defenses and also activate immune system cells such as macrophages.
Step-by-step explanation:
Interferons are cytokines released by virally infected cells and serve an essential role in the immune response. They act as messengers to warn nearby uninfected cells of a viral invasion, prompting the production of protective compounds to inhibit viral replication. Moreover, interferons also enhance the immune system function by activating macrophages and other cells involved in the defense against pathogens.