Which group had the second-highest usage during the same period?

• A. Primates
• B. Dogs
• C. Cats
• D. Rabbits

Answer: (A)

The idea being tested is how to read a period-specific usage ranking across species. If primates are the second-highest, that means one other group had more animals used, and primates had more usage than the remaining groups. Nonhuman primates are often chosen when the research question needs a close physiological and immunological similarity to humans, such as in neuroscience, vaccine and infectious disease work, or translational studies. This makes their usage relatively high compared with other common lab animals, though not the top group in that period. The other species mentioned are used widely as well, but their totals were lower than primates for that timeframe, which is why primates occupy the second spot.