Scientists believe that, unlike most other species of barnacle, turtle barnacles (Chelonibia testudinari) can dissolve the cement-like secretions they...

SOLUTION

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

• Scientists believe
  • that, unlike most other species of barnacle,
    • turtle barnacles (Chelonibia testudinari)
      • can dissolve
        • the cement-like secretions
          • they use to attach [?] to a sea turtle shell,
  • enabling the barnacles
    • to move short distances across the shell's surface.

• The blank choices: it / themselves / them / itself

Understanding the Meaning

The sentence starts by telling us what scientists believe:

• Unlike most other barnacle species,
• turtle barnacles can dissolve the cement-like secretions...

Now let's see what these secretions are for:

• "they use to attach ______ to a sea turtle shell"

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

• it, themselves, them, itself

To see what works here, let's understand what's being attached!

The barnacles use these secretions - but for what purpose?

• To attach something to a sea turtle shell

Now let's think about this logically:

• What would barnacles be attaching to the shell?
• The barnacles themselves! They're sticking themselves onto the turtle's shell.

So the complete picture is:

• Barnacles produce cement-like secretions
• They use these secretions to attach themselves to turtle shells
• Unlike other barnacles, turtle barnacles can dissolve these secretions
• This allows them to move around on the shell

What do we notice about the structure here?

• The barnacles are doing the attaching - they're the subject performing the action
• The barnacles are also what's being attached - they're also the object of the action
• When the subject and object are the same thing (the barnacles are attaching the barnacles), we need a reflexive pronoun - one that points back to the subject
• Since "barnacles" is plural, we need the plural reflexive form

So we need themselves - it's plural (matching "barnacles") and reflexive (showing that they're attaching themselves, not something else).

The correct answer is Choice B: themselves.

GRAMMAR CONCEPT APPLIED

Reflexive Pronouns: When the Subject Acts on Itself

When the subject of a sentence performs an action on itself (meaning the subject and object are the same entity), we use a reflexive pronoun (called reflexive because it reflects back to the subject):

Singular reflexive pronouns: myself, yourself, himself, herself, itself
Plural reflexive pronouns: ourselves, yourselves, themselves

Pattern to recognize:

• Subject and object are different:
  The barnacles attach other organisms to the shell. (would use "them" for other organisms)
• Subject and object are the same (reflexive):
  The barnacles attach themselves to the shell. (must use "themselves")

The reflexive pronoun must match its antecedent in number:

• The barnacle attaches itself (singular)
• The barnacles attach themselves (plural)

In this question:

• Antecedent: "turtle barnacles" (plural)
• Action: attaching (done by the barnacles to the barnacles)
• Since subject = object AND plural: themselves