Question 21·Hard·Boundaries
Through tireless nightlong observations, the astronomer Caroline Herschel discovered several _____ when her brother William was appointed royal astronomer, she continued to assist him while also pursuing her own research.
Which choice completes the text so that it conforms to the conventions of Standard English?
For sentence-boundary questions, identify whether both sides form independent clauses. If they do, eliminate options that double up connectors (e.g., "; and"), misuse colons, or omit the comma before a coordinating conjunction. Choose the option that cleanly follows these rules while preserving the intended meaning.
Hints
Find the two main actions
Identify the two core statements: what Herschel did first and what she did later. Are both full sentences by themselves?
Recall joining rules
When two independent clauses are joined in one sentence, use either a semicolon or a comma plus a coordinating conjunction (FANBOYS).
Focus on punctuation before "and"
Each option includes "and" but uses different punctuation before it. Which pattern correctly connects two complete clauses?
Avoid doubled or misused punctuation
Is it standard to combine a semicolon or a colon with a coordinating conjunction like "and" in the middle of a sentence?
Step-by-step Explanation
Identify the clause structure
There are two main actions: (1) the astronomer Caroline Herschel "discovered several comets" and (2) "she continued to assist him while also pursuing her own research." The second action is preceded by a dependent clause beginning with "when." Thus, we have two independent clauses (the second is introduced by a dependent clause).
Recall correct ways to join independent clauses
Independent clauses within one sentence can be joined by a period (making two sentences), a semicolon, or a comma plus a coordinating conjunction (FANBOYS). Since all choices use "and," the key is the punctuation immediately before it.
Eliminate misused patterns
- "comets; and" is nonstandard because a semicolon already joins independent clauses; it should not be combined with a coordinating conjunction.
- "comets: and" misuses a colon; colons introduce explanations, lists, or restatements and are not paired with "and" like this.
- "comets and" (no comma) leaves two independent clauses joined only by a coordinating conjunction, which on the SAT requires a comma.
Choose the correct option and confirm the reading
A comma plus the coordinating conjunction correctly joins the two independent clauses: "Through tireless nightlong observations, the astronomer Caroline Herschel discovered several comets, and when her brother William was appointed royal astronomer, she continued to assist him while also pursuing her own research." Therefore, the correct answer is comets, and.