单选题 Microbes, also called microorganisms, are minute living things that individually are usually too small to be seen with the unaided eye.

单选题 HIV infection and AIDS, starting from obscurity, rose to become a leading cause of death in the United States by 1993.

单选题 Soil microbes help break down wastes and incorporate nitrogen gas from the air into organic compounds, thereby recycling chemical elements in the soil, water and air.

单选题 There are recent reports dating HIV to the early twentieth century, but it didn’t appear to take off until midcentury.

单选题 We tend to associate these small organisms only with major diseases such as AIDS, uncomfortable infections, or such common inconveniences as spoiled food.

单选题 Hospital workers must be able to protect patients from common microbes that are normally harmless but pose a threat to the sick and injured.

单选题 Cholera was, of course, a very big concern in the nineteenth century and remains a concern today, especially in places like Bangladesh.

单选题 The system of nomenclature for organisms in use today was established in 1735 by Carolus Linnaeus.