Final answer:
The correct answer to the question is 'B. Large; 1', which refers to the number of cases expected if a large number of people were given a 1 mSv dose of radiation per year.
Step-by-step explanation:
Risk estimates for radiation exposure are typically given in terms of the number of cases expected if a large number of people were given a certain dose of radiation per year. According to the information provided, a dose of 1 mSv per year increases a person's annual risk of dying from radiation-induced cancer by 10 in a million, and this continues for about 30 years. Based on the linear hypothesis, the risk is directly proportional to the dose, meaning that a larger group's results would be more statistically significant than a smaller group's. Considering both the given information and the linear hypothesis, the correct answer to the student's question would be 'B. Large; 1', meaning that risk estimates are given in the number of cases expected if a large number of people were given a 1 mSv dose per year.