Recent pollen analyses of the Aran Islands have led some researchers to propose that the now treeless islands were once...

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

Sentence 1:

• Recent pollen analyses of the Aran Islands
  • have led some researchers
    • to propose
      • that the now treeless islands were once wooded.

Sentence 2:

• This hypothesis [?]
  • that certain trees,
    • such as P. sylvestris,
  • survived without interruption or human intervention throughout the Holocene
• cannot stand,
  • researchers Michael O'Connell and Karen Molloy counter,
  • unless other explanations can first be ruled out.

Understanding the Meaning

Let's start from the beginning:

The first sentence tells us:

• Recent pollen analyses have led researchers to propose something—
  • that the now treeless Aran Islands were once wooded (had trees).

So researchers are making a claim based on pollen evidence.

Now the second sentence starts:

• "This hypothesis ______..."

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

• A. suggesting
• B. suggested
• C. suggests
• D. has suggested

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

The sentence continues:

• "...that certain trees, such as P. sylvestris, survived without interruption or human intervention throughout the Holocene cannot stand, researchers Michael O'Connell and Karen Molloy counter..."

Now let's understand what this structure is telling us:

• The phrase "that certain trees... survived throughout the Holocene"
  • describes what the hypothesis is about—
  • it's adding detail about WHICH hypothesis we're talking about

• Then we get "cannot stand"
  • This is what the sentence is fundamentally saying
  • The hypothesis CANNOT STAND (meaning it fails, it doesn't hold up)

• "researchers Michael O'Connell and Karen Molloy counter"
  • This tells us WHO is saying this hypothesis cannot stand

So the complete picture is:

• The main point of the sentence is that the hypothesis "cannot stand"
• The part about "certain trees survived" is describing which hypothesis

What do we notice about the structure here?

• "Cannot stand" is the main verb—the primary action of the sentence
• We need the blank to create a describing phrase, not another main verb
• If we used "suggests" or "suggested" or "has suggested," we'd have TWO main verbs competing with each other: one at the blank and "cannot stand"
• We need a form that DESCRIBES the hypothesis rather than acting as a separate main verb

So we need suggesting—this creates a descriptive phrase "hypothesis suggesting that..." which tells us what kind of hypothesis, while keeping "cannot stand" as the only main verb.

The correct answer is A. suggesting.

GRAMMAR CONCEPT APPLIED

Using Participle Phrases vs. Main Verbs

When you have a long subject that needs description before reaching the main verb, you use a participle (a verb form ending in -ing or -ed) to add descriptive information without creating a competing main verb:

Pattern: Subject + participle phrase (description) + main verb

Example 1:

• Wrong: "The theory suggests a new mechanism cannot be proven"
• Problem: Two main verbs ("suggests" and "cannot be proven")

• Correct: "The theory suggesting a new mechanism cannot be proven"
• "suggesting a new mechanism" = descriptive phrase (participle phrase in grammar terms)
• "cannot be proven" = main verb

Example 2:

• Wrong: "The proposal recommended changes was rejected"
• Problem: Two main verbs competing

• Correct: "The proposal recommending changes was rejected"
• "recommending changes" = describes which proposal
• "was rejected" = main verb

In this question:

• Subject: "This hypothesis suggesting that certain trees survived..."
• The participle "suggesting" starts a descriptive phrase
• Main verb: "cannot stand"
• This is what the sentence is actually saying about the hypothesis

The key is recognizing when the sentence needs a description of the subject (use a participle) versus when it needs the main action (use a finite verb).