Question 97·Easy·Boundaries
Many migratory birds rely on Earth’s magnetic field to _____ scientists still do not fully understand how the birds sense the field.
Which choice completes the text so that it conforms to the conventions of Standard English?
For punctuation/boundaries items, first confirm whether both sides are independent clauses. If they are, identify the relationship (addition, contrast, cause/effect). Then apply the rule: place a comma before a coordinating conjunction (FANBOYS) joining two independent clauses; do not put the comma after the conjunction; avoid combining a semicolon with a FANBOYS conjunction.
Hints
Check each side of the blank
Cover the blank and verify whether the words before it will form a complete clause once completed, and that the words after it form a complete clause.
Consider the meaning relationship
Determine whether the two parts add information, cause an effect, or show contrast.
Remember the FANBOYS comma rule
When two independent clauses are joined by a coordinating conjunction (for, and, nor, but, or, yet, so), place a comma before the conjunction.
Eliminate nonstandard punctuation patterns
Watch for missing commas before conjunctions, commas placed after conjunctions, and semicolons used together with a coordinating conjunction.
Step-by-step Explanation
Identify the clauses on each side of the blank
Read the text before and after the blank as if the blank were just a space.
- Before the blank: "Many migratory birds rely on Earth’s magnetic field to" — this sets up an infinitive; the needed verb phrase will complete the thought.
- After the blank: "scientists still do not fully understand how the birds sense the field" — this has a subject (scientists) and a verb phrase (do not fully understand) and expresses a complete thought.
The completed sentence will connect two independent clauses: one ending with "navigate" and the second beginning with "scientists."
Decide the relationship between the clauses
The first clause states that birds successfully use Earth’s magnetic field to navigate. The second states that scientists do not fully understand how birds sense the field. This is a contrast, so a coordinating conjunction like "yet" (similar to "but") is appropriate.
Recall the punctuation rule for coordinating conjunctions
When two independent clauses are joined by a coordinating conjunction (FANBOYS: for, and, nor, but, or, yet, so), place a comma before the conjunction and do not place a comma after it. A semicolon is used between independent clauses without a coordinating conjunction (often with a conjunctive adverb like "however"), not with a FANBOYS conjunction.
Apply the rule to the choices
Test each option:
- "navigate yet" omits the required comma before a coordinating conjunction joining two independent clauses.
- "navigate yet," misplaces the comma after the conjunction instead of before it.
- "navigate; yet" combines a semicolon with a coordinating conjunction, which is not standard in this context.
Only "navigate, yet" correctly places the comma before the coordinating conjunction. So the completed sentence is:
"Many migratory birds rely on Earth’s magnetic field to navigate, yet scientists still do not fully understand how the birds sense the field."