Question 144·Hard·Boundaries
In a recent lecture on exoplanet atmospheres, astrophysicist Marisol Vega described the discovery of ____ which is located only 1,150 light-years from Earth and exhibits an atmosphere rich in sodium.
Which choice completes the text so that it conforms to the conventions of Standard English?
In boundaries questions, identify what starts the text after the blank. If you see “which,” decide whether the clause is nonessential (extra information) or essential (needed to identify the noun). Nonessential “which” clauses require a comma before them; eliminate semicolons/periods because they require a full independent clause after them, and eliminate colons unless the next text is clearly a list, example, or explanation introduced by a complete sentence.
Hints
Find the keyword after the blank
Look at the first word after the blank. If it’s “which,” you’re probably dealing with a relative clause.
Check whether the information is extra or defining
Ask: does the “which …” part simply add extra detail about a specific noun, or is it necessary to identify the noun?
Match the clause type to punctuation
Nonessential “which” clauses are introduced with a comma. Semicolons connect two complete sentences; colons introduce explanations/lists after a complete sentence; periods end a sentence.
Step-by-step Explanation
Locate the clause after the blank
After the blank, the sentence continues with “which is located only 1,150 light-years from Earth and exhibits an atmosphere rich in sodium.” This is a relative clause beginning with which.
Decide whether the clause is essential
WASP-96b is a specific, named planet (a proper noun). The “which …” clause is adding extra, nonessential information about it (location and atmospheric composition), not defining which WASP-96b we mean.
Apply the punctuation rule
A nonessential “which” clause must be set off with a comma before it. A semicolon, colon, or period cannot correctly introduce a dependent “which” clause in this structure.
Select the choice that supplies the needed comma
The option that correctly places a comma before the “which” clause is WASP-96b,.