Why are rodents predominantly used in research?

• A. Their life span is long
• B. They are rare and expensive
• C. They make up more than 90% of research animals due to short life span, ease of breeding, and similarity to human biology
• D. They do not share biology with humans

Answer: (C)

The main idea here is that rodents dominate biomedical research because they are practical to study and biologically relevant models. Their short life span and quick generation times mean researchers can observe aging, disease progression, and the effects of interventions in a relatively short period, which is essential for efficient experimentation. Their ease of breeding leads to large, uniform groups of animals with predictable genetics, which helps keep studies controlled and reproducible.

Add to that, the biology they share with humans is substantial enough to model many human conditions. Mice and rats have similar organ systems and many conserved metabolic and genetic pathways, so findings often translate to humans. There are extensive genetic tools and well-established inbred strains that let scientists study gene function and model specific diseases precisely.

These factors together explain why rodents make up the vast majority of research animals. The other statements don’t fit because their life span is not long (it’s actually short), they are not rare or expensive (they’re relatively inexpensive and easy to house), and they do share biology with humans (which is why they’re used in the first place).