An environmental survey worker collects a water sample that contains radioactive material. The worker also uses intact sealed alpha, beta and gamma sources to check a radiation monitor, returning each source to a shielded container after the check.
Which event could cause the worker to remain exposed after leaving the survey area?
The worker watches the monitor while the sealed gamma source is checked.
The sealed alpha source ionises air beside the worker before it is returned.
The worker accidentally swallows some of the water sample.
The sealed beta source is briefly held near the worker's boots.