Reduction means that: researchers must use the smallest number of animals possible to achieve the research. researchers have to prove there is no alternative to using animals in research and that the use of animals is justified by the scientific or clinical value of the study. procedures must be modified to minimize discomfort , infection, illness, and pain of animals. researchers have to prove their research is reliable.

The correct answer is **procedures must be modified to minimize discomfort, infection, illness, and pain of animals.**<br /><br />The Three Rs of animal research ethics are Replacement, Reduction, and Refinement. While all the options presented relate to ethical considerations in animal research, only one accurately defines *Reduction*. Let's break down why:<br /><br />* **Reduction:** This specifically means minimizing the number of animals used in research while still obtaining statistically valid results. It's about using the *minimum* number necessary, not necessarily the *smallest* possible number. Sophisticated experimental design and statistical analysis are key to achieving reduction.<br /><br />* **Replacement:** This refers to using alternatives to animal models whenever possible, such as cell cultures, computer simulations, or human volunteers. The option mentioning proving there's no alternative describes Replacement, not Reduction.<br /><br />* **Refinement:** This focuses on minimizing pain, suffering, distress, and lasting harm experienced by animals used in research. This includes using appropriate anesthesia and analgesia, providing suitable housing and enrichment, and using humane endpoints. The correct answer describes Refinement.<br /><br />* **Proving research is reliable** is important for scientific validity but isn't directly related to the principle of Reduction.<br />