"When did the symptoms begin and how long have you had them?"

A) ​open-ended question
B) ​closed-ended question

This is an open-ended question because it allows for a detailed response, not limited to a yes/no or a single piece of information. It invites the respondent to explain in their own words the onset and duration of their symptoms, which cannot be captured by a simple yes or no or a single factual answer.