A comma question with the same words in every choice tests which words belong together and which add extra information. Read around the blank to find the main verb, then ask who or what it's about: that's the subject. Name the parts at each possible comma. Commas can go around extra information, but they can't separate a subject from its verb or a word from the that part that finishes it. A pause alone doesn't call for a comma.
Hints
- Hint 1
Read the last sentence past the blank and find its main verb.
- Hint 2
Ask what whole group of words answers “What is treated as stronger evidence?” Trace that subject to its end, including words that describe it.
- Hint 3
Look back at how Okafor weighs claims, and check what the description in the blank adds. Does it tell which records are meant, or give a side comment?
Step-by-step
Follow the subject and its description
Step 1Find the main verb
Past the blank, are generally treated as stronger evidence contains the main verb, are treated. What is being treated this way? The details are, so the details are the core of the subject, the words naming what is being treated. Only commas vary, so let's find where that whole subject ends.
- Step 2
Trace the full subject
Where does the subject end? It starts with The details in eyewitness and continues through the description of records backed up by port registers. Corroborate means back up with evidence, and surviving port registers are what do that. So corroborate is a verb inside the description, not the sentence's main verb. The subject extends through corroborate, right before are treated.
- Step 3
Decide whether the description is extra
Does the description add a side comment, or tell which records are meant? It's a that clause, a group of words with its own subject and verb. Okafor gives more weight to claims supported by independently created documents, so the clause tells which records have support. Removing it would make the claim about eyewitness records more general, leaving out the support that matters to Okafor.
- Step 4
Apply the comma rules
Shrink the whole subject to they: they are generally treated as stronger evidence. No comma goes between a subject and its verb, so none belongs after corroborate. Records stays attached to the that clause that tells which records are meant, so none belongs after records. The version with no commas keeps both links. Choice D.