The activity that is described here falls under the category of C. Endorsing a candidate.
What happens in this category that has to do with endorsement
In this description, the representatives from the interest group are interviewing a candidate running for office to assess their stance on the group's position regarding nuclear plants.
If the candidate is in alignment with the group's position, the group would likely support or endorse this candidate.
Endorsing a candidate has to do with giving support, backing them up, or publicly expressing approval for a given candidate.