The correct option is C Penicillin does not work against viral infections.
Penicillin is an antibiotic which is used to treat bacterial infections. It blocks life processes in bacteria which are used to build bacterial cell wall. Viruses do not have any pathways for building cell wall. Hence, it is not effective in treating a viral infection like influenza. Human cells are not affected if penicillin is consumed because they do not have cell wall.