A model created by biologist Luis Valente predicts that the rate of speciation—the rate at which new species form—on an...

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

• A model
  • created by biologist Luis Valente
  • predicts that
    • the rate of speciation—
      • the rate at which new species form—
      • on an isolated island
        • located approximately 5,000 kilometers from the nearest mainland
    • [?]
    • triple the rate of speciation
      • on an island only 500 kilometers from the mainland.

Understanding the Meaning

Let's start reading from the beginning:

'A model created by biologist Luis Valente predicts that...'

So we have a scientific model that makes a prediction. What does it predict?

'...the rate of speciation—the rate at which new species form—'

We're talking about speciation (how new species form) and specifically the rate at which this happens. The dashes give us a quick definition.

'...on an isolated island located approximately 5,000 kilometers from the nearest mainland'

So we're focusing on the speciation rate on a very isolated island - one that's far from any mainland.

This is where we have the blank.

Let's look at the choices:

• A. being
• B. to be
• C. to have been
• D. will be

These are all different forms of the verb "be." To see what works here, let's read the rest of the sentence and understand what it's saying!

The sentence continues: 'triple the rate of speciation on an island only 500 kilometers from the mainland.'

So the complete prediction is:

• The model predicts that the speciation rate on a far island (5,000 km from mainland) will be triple (three times) the speciation rate on a near island (500 km from mainland)

What do we notice about the structure here?

After "predicts that," we have a complete clause that needs its own verb:

• The subject of this clause is "the rate of speciation...on an isolated island"
• This subject needs a verb that can stand on its own - a complete verb form

Looking at our choices:

• "being" is a participle - it can't be the main verb of a clause
• "to be" is an infinitive - it can't be the main verb after "predicts that"
• "to have been" is also an infinitive - it can't be the main verb here either
• "will be" is a complete verb in future tense

Since this is a prediction about what will happen, we need a future tense verb.

The correct answer is D. will be

The structure works like this: "A model predicts that [the rate on far island] will be triple [the rate on near island]."

GRAMMAR CONCEPT APPLIED

Complete Verbs After "That" Clauses

When you use verbs like "predicts," "says," "believes," "thinks," or "claims" followed by "that" to introduce what someone predicts/says/believes, the clause after "that" needs its own complete verb (called a finite verb in grammar terms):

Pattern:

• Subject + predicting verb + that + [new subject + complete verb + rest of information]
• The model predicts that + [the rate will be triple]
• The scientist believes that + [the results are accurate]
• The study claims that + [the effect was significant]

What DOESN'T work:

• Participles: being, having, going (these describe or modify but can't be main verbs)
• Infinitives: to be, to have been, to go (these need helping structures)

What DOES work:

• Complete verbs that show tense: will be, is, was, does, can be, might be, etc.

In this question:

• "A model predicts that the rate will be triple"
• NOT "A model predicts that the rate being triple"
• NOT "A model predicts that the rate to be triple"

The verb form must match the logic of the sentence. Since "predicts" indicates a prediction about the future, "will be" (future tense) makes perfect sense.