The growing field of underwater archaeology relies on teams of specialized researchers who document shipwrecks and submerged settlements—some of whom,...

Let's begin by understanding the meaning of this sentence. We'll use our understanding of pause points and segment the sentence as shown - understanding and assimilating the meaning of each segment bit by bit!

Sentence Structure

• The growing field of underwater archaeology
  • relies on teams of specialized researchers
    • who document shipwrecks and submerged settlements—
      • some of whom,
        • like maritime historian Dr. Chen Watanabe,
      • [?] innovative sonar technology
        • to map sites that are too deep or dangerous
          • for traditional excavation methods.

Understanding the Meaning

Let's start reading from the beginning:

The passage tells us about underwater archaeology as a growing field:

• It 'relies on teams of specialized researchers'
• These researchers 'document shipwrecks and submerged settlements'

Now we get a dash, which signals additional information is coming:

• 'some of whom, like maritime historian Dr. Chen Watanabe...'

This is where we have the blank.

Let's look at our choices:

• uses (singular)
• use (plural)
• has used (singular)
• is using (singular)

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

The complete phrase is:

• 'some of whom, like maritime historian Dr. Chen Watanabe, _____ innovative sonar technology to map sites that are too deep or dangerous for traditional excavation methods.'

Now let's understand what this is telling us:

• 'some of whom'
  • 'whom' refers back to the 'researchers' we just mentioned
  • So this means 'some of the researchers'

• 'like maritime historian Dr. Chen Watanabe'
  • This is just giving us an example of one of these researchers
  • It's set off by commas because it's extra information

• The action these researchers perform:
  • They use innovative sonar technology
  • Purpose: to map sites that are too deep or dangerous for traditional excavation

What do we notice about the structure here?

• The subject of our blank verb is 'some of whom'
  • 'whom' refers back to 'researchers' (which is plural)
  • 'some of the researchers' is a plural subject

• The phrase 'like maritime historian Dr. Chen Watanabe' might seem like it could be the subject
  • But it's set off by commas on both sides
  • This tells us it's just an example - not the main subject
  • The true subject is still 'some of whom' (plural)

• We need a verb that matches a plural subject
  • The simple present tense makes sense here - we're describing what these researchers do as their general practice

So we need the plural verb form: use (Choice B).

GRAMMAR CONCEPT APPLIED

Matching Verbs to Their True Subject (Subject-Verb Agreement)

When verbs are separated from their subjects by extra information, you need to identify the true subject to choose the correct verb form. Here's the key pattern:

The Principle:

• Find the true subject (who/what is performing the action)
• Ignore interruptive phrases set off by commas or dashes
• Make the verb agree with that subject in number (singular or plural)

Pattern 1: 'Some of [plural noun]' takes a plural verb

• Some of the students are studying abroad
• Some of the students is studying abroad
• The word 'some' here refers to multiple students, so it's plural

Pattern 2: Phrases set off by commas don't change the subject

• The manager, along with her assistants, reviews all applications
• The manager, along with her assistants, review all applications
• The subject is 'the manager' (singular) - 'along with her assistants' is extra information

Pattern 3: Relative pronouns (who/whom/that) take their number from what they refer to

• The researchers who work in the Arctic face harsh conditions
• One researcher who works in the Arctic faces harsh conditions
• 'who' matches the number of its antecedent (researchers = plural, researcher = singular)

In our question:

• Subject: 'some of whom' - 'whom' refers to 'researchers' (plural) - subject is plural
• Interruptive phrase: 'like maritime historian Dr. Chen Watanabe' - ignore for agreement purposes
• Correct verb: 'use' (plural form matching plural subject)