Which of the following organisms can be classified as genetically modified organisms?

Genetically modified organisms (GMOs) encompass a wide array of living entities that have been altered through genetic engineering techniques. The correct categorization includes bacteria, viruses, plants, and nonhuman animals because all these organisms can be modified at the genetic level to express desired traits or characteristics.

For example, bacteria are often genetically engineered in recombinant DNA technology to produce insulin or other pharmaceutical products. Viruses can also be modified for gene therapy purposes. In agriculture, plants such as corn and soybeans have been genetically engineered for traits like pest resistance or herbicide tolerance. Similarly, nonhuman animals, such as genetically modified mice or farm animals, have been created for research purposes or to enhance specific traits like faster growth rates in livestock.

This broad inclusion of different types of organisms reflects the versatility and applicability of genetic engineering across various fields, from medicine to agriculture, thus justifying why the correct answer encompasses all the mentioned categories.