Which of the following best defines a genetically modified organism (GMO)?

A genetically modified organism (GMO) is best defined as an organism that has been altered to contain foreign DNA. This alteration typically involves the insertion of genes from different species into the DNA of the target organism to enhance desired traits such as increased resistance to pests, improved nutritional content, or greater adaptability to environmental conditions. The use of biotechnology allows scientists to precisely manipulate an organism's genetic material, resulting in changes that would not occur through traditional breeding methods.

The other options, while related to genetics and breeding practices, do not accurately depict what constitutes a GMO. For instance, an organism with all natural genes lacks the foreign DNA characteristic of GMOs, and selective breeding involves choosing parent organisms with desirable traits to reproduce, which does not necessarily involve direct gene manipulation at the molecular level. Additionally, stating that an organism is created entirely in a laboratory oversimplifies the process and overlooks those GMOs that are developed through field trials and subsequent testing in natural environments. Thus, the defining feature of GMOs is the introduction of foreign DNA, distinguishing them from organisms created through other methods.