A punctuation question with an added description tests whether you can separate extra information from the main sentence. Look for a mark that opens or closes the description, then cross out the description to see whether a complete sentence remains. If it does, it's an insert, or extra information. An insert in the middle needs matching commas, matching dashes, or parentheses, so check both ends rather than stopping when you find one mark.
Hints
- Hint 1
Look for the subject and main verb on either side of the blank. Which person does the verb belong to?
- Hint 2
Test whether the added description can be removed. Then find both ends of the removable words and check how extra information is marked in the middle of a sentence.
Step-by-step
Cross out the description
Step 1Find the name and verb
Read back from the blank to the comma in In the 1930s,. It finishes the opening time phrase, so it isn't one end of a description of Inge. Now look at geophysicist Inge and discovered: they give us the person and her main verb, the word that tells what she did. The blank falls between them, so this question asks how the added words can fit there without breaking the sentence.
- Step 2
Test the added description
Every choice completes Inge's name with Lehmann and adds a Danish scientist, so let's test that description. Can we cross it out and still have a complete sentence? Without it, geophysicist Inge Lehmann discovered that Earth's core has a solid inner layer, and the rest of the sentence gives more detail about that layer. The sentence still has its main verb, discovered, and gives a complete thought, so the description is an insert, or extra information. It starts after her full name and ends before discovered, where the main sentence picks up again.
- Step 3
Mark both ends
For an insert in the middle of a sentence, the punctuation must open and close it with matching marks. Which version marks both ends here? Put a comma after Lehmann to start the insert and one after scientist to end it before discovered. The version with both commas marks both ends of the extra description. Choice C.