Question

all voters can participate in what kind of primary?
integrated
underground
open
absentee

Explanation:

In the context of primary elections, an open primary allows all registered voters (regardless of their party affiliation) to participate. "Integrated" is not a standard primary type in this context, "underground" is irrelevant, and "absentee" refers to a method of voting (not a primary type's defining participation rule). So the correct option is the one related to open primary.

Answer:

C. open