单项选择题

Questions 17 to 20 are based on the following passage. At the end of the passage; you will be given 20 seconds to answer the questions. Now, listen to the passage.
What would be considered the most reliable data in genealogical research

A.A birth record from a city hospital
B.A personal letter signed by a family member
C.An individual’s diary
D.A story told by a relative