A punctuation question with an -ing phrase tests how a complete thought connects to nearby words. First, find the point where the punctuation changes, then check what each part does by finding its subject and main verb. A period or semicolon needs full sentences on both sides; a comma sets off extra information, while words needed to complete the thought stay attached without one. Check whether each part can stand alone or needs the words beside it.
Hints
- Hint 1
Before the blank, the sentence is about Bell Burnell's analysis. Find what that analysis did, then decide where that thought becomes complete.
- Hint 2
Check whether the words about the Nobel Prize can stand alone. How does “even though she herself was excluded” connect to those words?
- Hint 3
Read the Nobel Prize phrase with the discovery statement. Ask whether it completes that thought or adds something after the thought is already complete.
Step-by-step
Compare the marks, then split
Step 1Compare the sentence breaks
The choices finish led to the discovery of and change the mark before earning, so we're testing whether a new sentence can start there. What do the semicolon version and the period version need? Both need full sentences on each side. Let's split the sentence at earning and check whether each side has a subject and a main verb.
- Step 2
Test whether both sides stand alone
Can each side stand alone? Before earning, “analysis of radio-telescope data led” gives us a subject, analysis, and a main verb, led, which says what the subject did. The word earning has no helper such as was, so it isn't a main verb. The words even though she herself was excluded from the award depend on the rest of the sentence, so was excluded can't make the earning phrase stand alone. The words from earning onward can't stand alone.
- Step 3
Attach the added result
What does the earning phrase add? The main thought is complete at pulsars in 1967, and earning adds the discovery's result: it brought her senior colleagues a Nobel Prize. One comma sets off this added result, and the period ends the phrase along with the sentence. The version with no punctuation doesn't set off that extra result, so use pulsars in 1967, earning. Choice D.