Several advantages—the ability to react strongly with chip components, to avoid interference from other waves, and to be confined within...

Sentence Structure

• Several advantages—
  • the ability to react strongly with chip components,
  • to avoid interference from other waves,
  • and to be confined within tiny circuits—
  ______ acoustic waves as a promising alternative
  • to electrical waves
    • for transmitting data on computer chips;
• as a result,
  • researchers are invested in developing more acoustic wave–based chips.

Understanding the Meaning

Let's start reading:

• 'Several advantages—'
  • This introduces the subject - we're talking about advantages (more than one).
• 'the ability to react strongly with chip components, to avoid interference from other waves, and to be confined within tiny circuits—'
  • These dashes set off a list that tells us WHAT those advantages are.
  • Three specific abilities are listed here.
  • After this list, the second dash closes, and we return to the main sentence.

This is where we have the blank. Let's look at the choices:

1. have positioned
2. positioning
3. by positioning
4. having positioned

To see what works here, let's read the rest of the sentence and understand what it's saying:

• '______ acoustic waves as a promising alternative to electrical waves for transmitting data on computer chips'
  • This is saying that these advantages do something to acoustic waves—
  • they establish or place them as a promising alternative.
• The second sentence adds: 'as a result, researchers are invested in developing more acoustic wave–based chips.'
  • This confirms the consequence - because of these positioning advantages, researchers are pursuing this technology.

What do we notice about the structure here?

• 'Several advantages' is the subject of the sentence
  • It's plural (more than one advantage)
  • Even though there's a long descriptive list between the dashes, 'Several advantages' is still the subject that needs a verb.
• The sentence needs a main verb - the action that the subject performs
  • The meaning is that these advantages have positioned (or established) acoustic waves as promising.
  • This verb needs to match with 'Several advantages' (plural).

So we need a complete main verb that agrees with the plural subject.

The correct answer is A. have positioned.

• 'Have positioned' is a complete verb form (present perfect tense)
• 'Have' agrees with the plural subject 'Several advantages'
• It serves as the main verb the sentence needs to be complete

GRAMMAR CONCEPT APPLIED

Main Verbs and Finite Verb Forms

Every complete sentence must have a finite verb—a verb form that shows tense and can agree with the subject (called the main verb). Participle forms like -ing words or having + past participle cannot serve as main verbs by themselves.

Pattern with finite verb (complete sentence):

• Subject: Several advantages
• Main Verb: have positioned
• Complete thought: "Several advantages have positioned acoustic waves as promising"

Pattern with participle (incomplete - fragment):

• Subject: Several advantages
• Participle only: positioning (or having positioned, or by positioning)
• Incomplete: "Several advantages positioning acoustic waves..."
• This lacks a finite verb and doesn't express a complete thought

Why this matters for subject-verb agreement:

• Finite verbs must agree with their subjects in number
• "Several advantages" = plural subject → needs "have positioned" (plural form)
• Not "has positioned" (singular form)

Application to this question:

The dashes create a long interruption between the subject "Several advantages" and where the verb needs to go. But once we identify that "Several advantages" is the subject, we know we need:

1. A finite verb (not a participle)
2. One that agrees with the plural subject
3. "Have positioned" is the only choice that meets both requirements