Question 206·Medium·Form, Structure, and Sense
Film critics often study director Alfred Hitchcock’s concept of the “MacGuffin,” a narrative device that _____ to propel the plot forward while remaining largely unexplained.
Which choice completes the text so that it conforms to the conventions of Standard English?
For subject–verb agreement questions in relative clauses (clauses starting with "that," "which," or "who"), first locate the noun that the relative pronoun refers to—that noun is your true subject. Ignore any words that come between the subject and the verb. Then decide whether the subject is singular or plural and choose the matching verb form. Finally, check that the verb tense and aspect match the sentence’s time frame and purpose (general truth vs. specific event), and prefer the simple, concise form when describing definitions or general characteristics.
Hints
Find what the blank is referring to
Look at the phrase "a narrative device that _____ to propel the plot forward." What word does "that" refer back to, and is that word singular or plural?
Focus on subject–verb agreement
Once you know the subject of the verb in the blank, decide whether the verb should be singular or plural to match that subject.
Check the time frame and style
Is this sentence describing a specific one-time event, or a general description/definition? Which verb tense and form best fits that kind of statement?
Step-by-step Explanation
Understand the sentence meaning
Read the full sentence:
"Film critics often study director Alfred Hitchcock’s concept of the 'MacGuffin,' a narrative device that _____ to propel the plot forward while remaining largely unexplained."
The sentence is making a general statement about what a MacGuffin is and how it functions in stories.
Identify the subject of the missing verb
The blank is inside the clause that begins with "that":
"that _____ to propel the plot forward..."
This is a relative clause describing "a narrative device."
So the subject of the verb in the blank is "a narrative device", which is singular.
Determine the correct verb form and tense
Because the subject "device" is singular, the verb in the blank must also be singular.
Also, the sentence describes a general, timeless characteristic of a MacGuffin (what it typically does in stories), so the verb should be in the simple present tense, which is standard for general truths and definitions.
Match the correct choice
Now check which option is a singular verb in the simple present tense and fits smoothly after "that":
- "serve" is plural.
- "have served" is plural and present perfect.
- "is serving" is present progressive.
- "serves" is singular simple present.
The only choice that correctly matches the singular subject "device" and the general, timeless statement is "serves", so the correct answer is B) serves.