Miya and Zach Were Discussing Whether Coffee Improves Concentration

Miya and Zach were discussing whether coffee improves concentration. Miya told Zach that caffeine did help because a friend of hers usually had trouble concentrating during tests, but one time when her friend drank coffee before taking a test, the friend had no trouble concentrating-and even scored an A on the exam. Which kind of evidence is Miya using?

A) An anecdote
B) A statement of authority
C) A commonsense belief
D) Empirical evidence