Answer:
b). Anecdote.
Explanation:
As we know, an anecdotal evidence is characterized as the limited evidences that relies mostly upon the personal testimonies. Such evidences are characterized as the limited selection of examples which support or refute an argument although they are not supported by scientific or statistical analysis. In the given example, Martha uses an 'anecdote' as the source of her information as it is based on her personal testimony('by relating the story of her ancestor who traveled across the United States in a covered wagon'). Thus, option B is the correct answer.
