The 2019 study published in Marine Biology explores the symbiotic relationships that develop when a coral reef and _____ (parrotfish,...

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 2019 study published in Marine Biology explores
  • the symbiotic relationships
    • that develop
      • when a coral reef and (?) three (?) interact
        • within a shared ecosystem.
• The research demonstrates
  • how each species contributes to the reef's health
    • while benefiting from the protection and resources it provides.

Understanding the Meaning

Let's read from the beginning:

"The 2019 study published in Marine Biology explores the symbiotic relationships that develop when a coral reef and..."

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

• "a coral reef and ___ three ___"

Let's look at our choices and see what we're deciding:

• "it's" vs "its"
• "inhabitant's" vs "inhabitants"

The parenthetical tells us what these three things are:

• (parrotfish, sea urchins, and cleaner shrimp)

So the sentence is saying:

• A coral reef and [something about] three creatures interact together.

What relationship is being described?

• These three creatures belong to the reef - they're the reef's inhabitants
• So we need the possessive form: "its" (belonging to it)
• NOT "it's" which would mean "it is" - test it: "a coral reef and it is three..." doesn't work!

And what about the second part?

• We're naming three creatures that ARE inhabitants
• We need the plural form: "inhabitants" (multiple inhabitants)
• NOT "inhabitant's" which would mean something belonging to one inhabitant

So we need: its three inhabitants

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

• "interact within a shared ecosystem"
• The second sentence tells us: "The research demonstrates how each species contributes to the reef's health while benefiting from the protection and resources it provides."

The complete meaning:

• The study looks at how a coral reef and its three inhabitants (the parrotfish, sea urchins, and cleaner shrimp) interact in their shared ecosystem
• It shows how they help each other - each species helps the reef stay healthy and gets protection and resources in return

The correct answer is Choice B: its three inhabitants

GRAMMAR CONCEPT APPLIED

Distinguishing Possessive "Its" from Contraction "It's" and Using Plural vs. Possessive Forms

This question tests two important concepts:

1. Its vs. It's:

• "Its" = possessive pronoun (belonging to it)
• Example: The dog wagged its tail. (the tail belongs to the dog)
• In our question: The reef has its inhabitants (the inhabitants belong to the reef)

• "It's" = contraction of "it is" or "it has"
• Example: It's raining outside. (It is raining)
• Test by expanding: If you can substitute "it is" or "it has," use "it's"

2. Plural Nouns vs. Possessive Forms:

• Plural noun = multiple things (add -s)
• Example: three inhabitants, five students, many books
• Use when you're simply naming multiple things

• Possessive form = ownership (add 's or s')
• Example: the inhabitant's home (the home of one inhabitant)
• Example: the inhabitants' homes (the homes of multiple inhabitants)
• Use when something belongs to the noun

In this question:

• We need "its" because the inhabitants belong to/are associated with the reef (possessive relationship)
• We need "inhabitants" because we're naming three creatures that ARE inhabitants (plural noun), not referring to something that belongs to them