Question 229·Easy·Boundaries
In the early 1960s, mathematician Katherine Johnson calculated trajectories for NASA's Mercury _____ work was crucial to the success of astronaut John Glenn's 1962 orbit of Earth.
Which choice completes the text so that it conforms to the conventions of Standard English?
For sentence-boundary questions, first determine whether the text on each side of the blank is an independent clause. If both sides are complete sentences and no conjunction is supplied, you typically need a semicolon or a period plus a capital letter. Eliminate choices that leave only a comma (comma splice), no punctuation (run-on), or incorrect capitalization after a period.
Hints
Check if each side can stand alone
Cover the blank and read the part before it, then the part after it. Ask yourself: could each part be its own complete sentence with a subject and a verb?
Think about how to separate two full sentences
If both sides are complete sentences, what punctuation is normally used between them when there is no joining word like "and" or "but"?
Pay attention to capitalization after a period
If you choose an option with a period, what should happen to the first letter of the word that follows it?
Watch out for comma splices and run-ons
Ask yourself: does this choice leave just a comma between two full sentences, or no punctuation at all? Both of those create errors.
Step-by-step Explanation
Identify the clauses on each side of the blank
Read the sentence in two parts, split at the blank:
- Before the blank (once filled): "In the early 1960s, mathematician Katherine Johnson calculated trajectories for NASA's Mercury missions" — subject ("mathematician Katherine Johnson") and verb ("calculated").
- After the blank: "her work was crucial to the success of astronaut John Glenn's 1962 orbit of Earth" — subject ("her work") and verb ("was").
So, you are connecting two independent clauses.
Recall how to connect two independent clauses
When two independent clauses are adjacent without a joining word (like "and" or "but"), you can:
- Use a semicolon between them.
- Use a period and start a new sentence with a capital letter.
- Use a comma plus a coordinating conjunction (not offered here).
A single comma alone is a comma splice; no punctuation is a run-on.
Test each answer choice against the rules
Check each option when inserted:
- Choice B "missions, her" yields: "... Mercury missions, her work was crucial ..." This is a comma splice between two independent clauses — incorrect.
- Choice C "missions. her" yields: "... Mercury missions. her work was crucial ..." A period must be followed by a capital letter to start a new sentence; "her" is lowercase — incorrect.
- Choice D "missions her" yields: "... Mercury missions her work was crucial ..." This fuses two independent clauses without punctuation — a run-on — incorrect.
- Choice A "missions; her" correctly uses a semicolon to join two closely related independent clauses without creating a comma splice, run-on, or capitalization error.
Therefore, the correct answer is A) missions; her.