Which of the following are examples of pure beta emitters?

The correct selection highlights examples of pure beta emitters, specifically isotopes that predominantly emit beta particles without significant accompanying gamma radiation. In this context, strontium-90 (90Sr) is a well-known pure beta emitter used in various applications, including cancer treatment and radiological research. It predominantly emits beta particles during its decay process.

Protactinium-32 (32Pa) also emits primarily beta particles, making it another good example of a pure beta emitter. The radioactive decay of these isotopes does not produce significant gamma radiation, which differentiates them from other radioactive materials that may emit multiple radiation types or primarily gamma radiation with secondary beta emissions.

The other options contain isotopes that are not considered pure beta emitters due to additional types of radiation they emit, particularly gamma rays, which complicates their classification as "pure" emitters. This is crucial for applications in medical dosimetry where the distinction between types of radiation is significant for treatment planning and risk assessment.