What percentage of animals used in medical research are cats and dogs?

• A. Fewer than one percent
• B. More than half
• C. About ninety percent
• D. None

Answer: (A)

The main idea here is how animal species are distributed in biomedical research. In practice, the vast majority of animals used are rodents—mice and rats—because they are inexpensive, easy to house, and there is a large toolkit of genetic and experimental methods already developed for them. Cats and dogs are used, but in far smaller numbers, making up well under 1% of animals used in most programs and reports. In the United States and many other regions, estimates place cats and dogs together at only a few tenths of a percent of all animals used. So the correct choice reflects this tiny share. The other options overstate their presence or suggest they’re negligible to the point of zero, which isn’t accurate.