The correct option is C Immunotherapy
Interferon-alpha (IFN-alpha) is a pleiotropic cytokine currently being used in cancer patients. It produces a long-lasting antitumor response or induces tumour immunity.
Radiotherapy is a treatment procedure for cancer, by ionizing radiation. Tumour cells are irradiated lethally. Thus by targeting the cancerous cells more than normal cells by taking care to direct radiation accurately by shielding, collimation and other means the tumour mass is destroyed.
Surgery is used to treat many types of cancer. Through methods like cryosurgery, laparoscopic surgery, laser surgery and electro-surgery and many new methods recently introduced, a surgeon removes the cancerous portion from the patient’s body.
In Chemotherapy, drugs are administered to target cells at different phases of the cell cycle during their cell division. Each time chemo is given, it tries to find a balance between killing the cancer cells (in order to cure or control the disease) and sparing the normal cells (to lessen side effects like the destruction of RBCs, loss of hair, scarring of the skin etc.). Apart from immunotherapy, none of them uses interferon-alpha.