Which option is NOT one of the 3 Rs?

• A. Replacement
• B. Refinement
• C. Reuse of animals
• D. Reduction

Answer: (C)

The three Rs in animal research ethics are Replacement, Reduction, and Refinement. Replacement means using non-animal methods or less sentient beings when possible. Reduction means using the smallest number of animals necessary by designing efficient studies and improving data analysis. Refinement means changing procedures to minimize pain, suffering, and distress, and to improve animal welfare. Reuse of animals isn’t one of these three principles; it’s not an official R. While reusing the same animal across studies might reduce the total number of animals used in some cases, the formal framework does not name it as a separate principle, and it can raise welfare concerns if it leads to cumulative distress.