The ability of some viruses to remain inactive (latent) for a period of time is exemplified by A) influenza, a particular strain of which returns every 10-20 years. B) herpes simplex viruses (oral or genital) whose reproduction is triggered by physiological or emotional stress in the host. C) Kaposi’s sarcoma, which causes a skin cancer in people with AIDS, but rarely in those not infected by HIV. D) the virus that causes a form of the common cold, which recurs in patients many times in their lives. E) myasthenia gravis, an autoimmune disease that blocks muscle contraction from time to time.