You are given a science question (easy-level) and four answer options (associated with "A", "B", "C", "D"). Your task is to find the correct answer based on scientific facts, knowledge, and reasoning. Do not generate anything else apart from one of the following characters: 'A', 'B, 'C', 'D'. There is only one correct answer for each question.

When a person is infected with the influenza virus, the immune system defends the body through a cell-mediated immune response. Which immune cell is responsible for protecting the body from the influenza virus infection?
(A) phagocytes (B) B lymphocytes (C) helper T lymphocytes (D) cytotoxic T lymphocytes
D