Read this sentence: "Pavlov, a Russian scientist, performed extensive research on dogs and is best known for his experiments in classical conditioning." What are the two commas doing?

1. Remove the part between the commas and the sentence still works: Pavlov performed extensive research on dogs. 2. That shows "a Russian scientist" is extra information dropped in to rename Pavlov. 3. Paired commas around a renaming phrase are doing exactly that job, option D. 4. Option A is the trap because commas often mark lists, but a list needs three or more items doing the same job, which is not the case here. 5. There is only one subject and no second complete statement, so option B fails as well. _Source: OpenStax Psychology 1e (CC BY 4.0), Ch 6 "Learning", section 6.2 Classical Conditioning_