Which set lists the primary SI units for activity, absorbed dose, dose rate, and dose equivalent correctly?

• A. Becquerel (Bq), gray (Gy), gray per hour (Gy/h), sievert (Sv)
• B. Curie (Ci), rad (rad), rem (rem), coulomb per kilogram
• C. Becquerel (Bq), gray (Gy), sievert (Sv), rem
• D. Curie (Ci), gray (Gy), gray per year (Gy/yr), rad

Answer: (A)

The main idea is using the SI units for each radiation quantity: activity, absorbed dose, dose rate, and dose equivalent. The correct set uses Becquerel for activity (disintegrations per second), gray for absorbed dose (energy deposited per kilogram), gray per hour for dose rate (how quickly that energy is deposited per unit mass), and sievert for dose equivalent (dose adjusted for biological effect). This keeps all four quantities in their standard SI units and matches how these measures are defined in radiation protection.

Why this is the best choice: Becquerel is the SI unit of activity, reflecting how many nuclear decays occur per second. The gray is the SI unit of absorbed dose, directly linking energy deposition to mass. For dose rate, using gray per hour expresses the rate at which energy is absorbed per kilogram, which is precisely what dose rate means. For dose equivalent, the sievert is the SI unit that accounts for the varying biological impact of different radiation types, making it the appropriate unit for comparing hazards.

Other options mix non-SI units or use units that represent related but different quantities. Curie, rad, and rem are older or non-SI units; substituting them means not using the standard SI framework for these four quantities. Using a unit like coulomb per kilogram corresponds to kerma, not absorbed dose, and Gy/yr instead of Gy/h is not the standard SI unit for dose rate.