Which of the Following Interpretations of Partisanship Is Correct

Which of the following interpretations of partisanship is correct?

A) Empirical research has demonstrated that most Americans change their partisanship frequently.
B) A party might be a shorthand cue for some voters but a source of personal identity for others.
C) Few Americans are willing to identify themselves as Republicans or Democrats and answer questions accordingly.
D) Scholars have no clear understanding of partisanship and the role it plays in American politics.