Question 225·Hard·Boundaries
The Hubble Space Telescope's primary mirror was found to be slightly _____ engineers devised an ingenious set of corrective optics that restored the telescope's full potential.
Which choice completes the text so that it conforms to the conventions of Standard English?
For boundaries questions, first determine whether each side of the blank is an independent clause. If both sides are independent clauses, choose among the three correct structures: comma + coordinating conjunction (FANBOYS), semicolon alone, or period with correct capitalization. Eliminate run-ons (no punctuation), semicolon + coordinating conjunction combos, and any option that breaks capitalization after a period.
Hints
Check completeness of each side
Look at the words before and after the blank. Does each side have its own subject and verb, forming a complete sentence?
Match the connector to the punctuation
If the word after the blank is the coordinating conjunction "so" (meaning “therefore”), what punctuation normally comes right before it when it links two complete sentences?
Be careful with semicolons
A semicolon can join two complete sentences by itself. If you use a semicolon, do you also need (or want) a coordinating conjunction like "so" right after it?
Check capitalization after a period
If you choose a period, what must be true about the first letter of the next sentence?
Step-by-step Explanation
Identify the clauses on each side of the blank
- Before the blank: "The Hubble Space Telescope's primary mirror was found to be slightly flawed" has a subject and verb, so it’s an independent clause.
- After the blank: "engineers devised an ingenious set of corrective optics that restored the telescope's full potential" also has a subject and verb, so it’s an independent clause.
You are connecting two independent clauses.
Use the correct pattern for joining independent clauses
To connect two independent clauses, you can use:
- comma + coordinating conjunction (FANBOYS, including so)
- semicolon (without a coordinating conjunction)
- period (to make two separate sentences, with correct capitalization)
Here, the word "so" is a coordinating conjunction, so the comma + conjunction pattern applies.
Eliminate choices that break punctuation/capitalization rules
- "flawed so": two independent clauses are joined without needed punctuation → run-on.
- "flawed; so": a semicolon should not be followed by a coordinating conjunction like "so" to join the same two clauses.
- "flawed. so": after a period, the next sentence must start with a capital letter; "so" is not capitalized.
Select the choice that correctly joins the clauses
The only option that correctly joins two independent clauses with the coordinating conjunction "so" is "flawed, so".