How Do Scholars Measure Partisanship

How do scholars measure partisanship?

A) by asking respondents in polls which party they voted for in the last election.
B) by asking respondents in polls whether they donated money to a candidate in the last election
C) by requiring respondents in polls submit to MRIs to measure deep cognitive attachments to the parties
D) by asking respondents a series of questions that place them on a 7-point scale