Question 21·Hard·Boundaries
Large-scale geological studies reveal that the Earth’s magnetic field has flipped polarity many _____ these reversals are recorded in the alignment of iron-rich minerals found in ancient lava flows.
Which choice completes the text so that it conforms to the conventions of Standard English?
For boundary questions, determine whether the text on both sides of the blank forms independent clauses. If it does and a conjunctive adverb like however is used to connect them, use the standard convention: a semicolon before the conjunctive adverb and a comma after it (...; however, ...). Eliminate commas that create comma splices and colons that don’t match the intended relationship.
Hints
Check for complete sentences
Look at the words before and after the blank. Can each side stand alone as a complete sentence with a subject and a verb?
Look for a conjunctive adverb
Scan the choices. Do you see a word like however, therefore, or consequently that signals a relationship between two complete sentences?
Use the standard pattern
If two independent clauses are being connected with a conjunctive adverb, recall the standard punctuation pattern: semicolon before the conjunctive adverb and a comma after it.
Step-by-step Explanation
Identify what’s on each side of the blank
Before the blank: Large-scale geological studies reveal that the Earth’s magnetic field has flipped polarity many ... is a complete thought with a subject (studies) and a main verb (reveal).
After the blank: these reversals are recorded in the alignment of iron-rich minerals found in ancient lava flows is also a complete sentence (subject = reversals, verb = are recorded).
Apply the rule for conjunctive adverbs
The word however is a conjunctive adverb. When it connects two independent clauses in one sentence, the standard pattern is:
So you need a semicolon before however and a comma after it.
Test the choices
times, however,leaves only a comma to separate two independent clauses (a comma splice).times; howeveris missing the comma after the introductory conjunctive adverbhowever.times: however,misuses a colon; a colon should introduce an explanation, list, or example.
Therefore, the choice that follows Standard English conventions here is times; however,.