Final answer:
The best kind of question to ask in order to learn how many listeners have heard of the Salem witch trials is Fixed alternative.
Step-by-step explanation:
The best kind of question to ask to learn how many listeners have heard of the Salem witch trials would be Fixed alternative. This type of question provides a set of pre-determined answer options for respondents to choose from. For example, you could ask listeners to select from options like 'Yes, I have heard of the Salem witch trials,' 'No, I have not heard of the Salem witch trials,' or 'I'm not sure.' This allows you to gather quantitative data and easily analyze the percentage of respondents who are familiar with the topic.