Which type of organism includes bacteria and viruses?

The correct choice is microorganisms or microbes because this term encompasses a wide variety of microscopic organisms, including both bacteria and viruses. Microorganisms are typically defined as organisms that are too small to be seen with the naked eye and include not only bacteria and viruses but also other entities such as fungi and protozoa.

Bacteria are single-celled organisms that can exist independently or in colonies, and they play various roles in ecosystems, including decomposition and nutrient cycling. Viruses, although they are often considered non-living entities because they require a host cell to replicate, are also classified under this umbrella due to their microscopic size and biological impact.

The other options are more exclusive: animals and plants are multicellular organisms that do not include bacteria and viruses within their classifications, whereas fungi, while classified as microorganisms, do not cover the broader group that includes bacteria and viruses. Hence, "microorganisms/microbes" is the most accurate and comprehensive answer to encompass both bacteria and viruses effectively.