The International Climate Research Consortium has published over forty studies on Arctic temperature patterns. Each one of these studies, which...

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 International Climate Research Consortium
• has published over forty studies on Arctic temperature patterns.
• Each one of these studies,
  • which span multiple decades
  • and include data from various research stations,
• (?) on a specific geographic region within the Arctic Circle,
• though several examine overlapping areas during different time periods.

Understanding the Meaning

The first sentence gives us the context:

• The International Climate Research Consortium has published over forty studies on Arctic temperature patterns.
  • So we're talking about a collection of over forty different studies.

Now the second sentence tells us something about these studies individually:

• 'Each one of these studies...'
  • This phrase is key - 'each one' means we're talking about the studies one at a time, considering them individually.
  • 'Each one' is the subject - the thing doing the action in this sentence.

Now here's where we need to fill in the blank:

• 'Each one of these studies ______ on a specific geographic region'

Let's look at our choices:

• We need to decide between:
  • have concentrated (plural)
  • were concentrating (plural)
  • concentrates (singular)
  • concentrate (plural)

What verb form works with 'each one'?

• 'Each one' is singular - it's talking about the studies one at a time
• So we need a singular verb: concentrates

Now let's read the rest to see the complete picture:

The sentence includes this descriptive part:

• 'which span multiple decades and include data from various research stations'
  • This is giving us extra information about 'these studies'
  • Notice it uses plural verbs (span, include) because it's describing the studies as a group
  • But this doesn't change what our main verb should be!

The sentence continues:

• 'though several examine overlapping areas during different time periods'
  • This adds a contrast - yes, each study focuses on one specific region,
  • BUT some studies happen to look at overlapping geographic areas, just during different time periods

What do we notice about the structure here?

The subject 'each one' is separated from its verb by quite a bit of text:

• First by the phrase 'of these studies'
• Then by the whole descriptive clause about spanning decades and including data

But the verb must still agree with the true subject:

• 'Each one' (singular) needs 'concentrates' (singular)
• Even though 'studies' (plural) appears right before the blank,
• And even though the descriptive clause uses plural verbs,
• Our verb must match 'each one'

So we need: concentrates (Choice C)

Grammar Concept Applied

Subject-Verb Agreement with Separated Subject and Verb

The verb must agree with the true subject, even when other words come between them. Two common patterns create this separation:

Pattern 1: Prepositional phrases

• The collection of ancient manuscripts is valuable
• Subject: "collection" (singular)
• "of ancient manuscripts" is a prepositional phrase
• Verb agrees with "collection," not "manuscripts"

Pattern 2: Descriptive clauses (called relative clauses in grammar terms)

• Each scientist who works at multiple laboratories presents findings annually
• Subject: "Each scientist" (singular)
• "who works at multiple laboratories" describes the scientist
• Verb agrees with "Each scientist," not with "laboratories"

In our question:

• Subject: "Each one" (singular)
• Separated by: "of these studies" + "which span multiple decades and include data from various research stations"
• Verb must agree with: "Each one" → concentrates (singular)

Key tip: The word "each" (and phrases like "each one") is always singular, even when followed by "of [plural noun]."