When a clause begins with a phrase such as “among the patterns,” check whether the subject appears after the verb. Temporarily remove introductory prepositional phrases, relative clauses, and parenthetical expressions; then identify the head noun of the true subject and choose a finite verb that agrees with it.
Hints
- Hint 1
Focus on the second clause
Examine only the text after the semicolon and determine what it needs to become an independent clause.
- Hint 2
Look beyond the opening phrase
The noun that controls the verb does not always appear before it. Find what is being identified as one of the documented patterns.
- Hint 3
Check both form and agreement
Choose a finite verb that agrees with the head noun of the clause’s subject.
Step-by-step
- Step 1
Identify the clause after the semicolon
The semicolon must be followed by an independent clause. The clause begins with the prepositional phrase “among the geographically distinctive patterns.”
- Step 2
Find the subject
Because the clause uses inverted word order, its subject appears after the blank: “a cluster of unusually narrow rings.” The head noun of this subject is the singular noun “cluster.”
- Step 3
Choose the appropriate verb
The clause needs a finite singular verb that agrees with “cluster.” Therefore, “is,” correctly completes the clause and supplies the first comma setting off “for example.”