French philosopher René Descartes doubted whether he could prove his own existence. Eventually, he found proof in his famous phrase...

Sentence Structure

Sentence 1:

• French philosopher René Descartes
  • doubted
    • whether he could prove his own existence.

Sentence 2:

• Eventually, he
  • found
    • proof
      • in his famous phrase 'I think, therefore I am.'

Sentence 3:

• The [?] simplicity
  • masks
    • [?] complexity:
• only those who exist
  • would be able to ponder their existence.

Understanding the Meaning

Let's start from the beginning to understand the full context:

First sentence:

• French philosopher René Descartes doubted whether he could prove his own existence.
  • This sets up the problem - Descartes was questioning whether he could prove he actually exists.

Second sentence:

• Eventually, he found proof in his famous phrase 'I think, therefore I am.'
  • Descartes solved his problem with ONE specific phrase (singular)
  • The phrase is: 'I think, therefore I am.'

Now we reach the blank in the third sentence:

• "The ______ complexity:"

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

• Is it "phrase" (singular) or "phrases" (plural)?
• Do we need an apostrophe (possessive)?
• Is the pronoun "its" or "their"?

From what we've read:

• The previous sentence mentions "his famous phrase" - just ONE phrase
• So we need the singular form: "phrase"
• The simplicity belongs TO the phrase
• So we need the possessive form: "phrase's" (with apostrophe + s)

Now for the pronoun, let's read the complete sentence to understand what it's saying:

• "The phrase's simplicity masks its/their complexity: only those who exist would be able to ponder their existence."

Let's understand what this means:

• "The phrase's simplicity"
  • The phrase 'I think, therefore I am' SEEMS simple
  • It's short and straightforward
• "masks its/their complexity"
  • "Masks" means hides or conceals
  • There's actually hidden complexity in this simple-looking phrase
• The colon explains what that complexity is:
  • "only those who exist would be able to ponder their existence"
  • This is the deep idea: you have to exist to think about whether you exist
  • That's actually quite profound and complex!

What do we notice about the pronoun?

• "Its" or "their" needs to refer back to something
• The sentence structure is: "The phrase's simplicity masks [the phrase's] complexity"
• We're talking about ONE phrase throughout
• So we need "its" (singular) to match "phrase" (singular)
• If we used "their" (plural), it wouldn't match the singular "phrase"

So the correct answer is: D. phrase's simplicity masks its

• "Phrase's" = singular possessive (the one phrase mentioned)
• "Its" = singular pronoun agreeing with "phrase"

GRAMMAR CONCEPT APPLIED

Possessive Forms and Pronoun Agreement Working Together

This question tests two important concepts that must work together:

1. Forming Possessives with Singular Nouns:

When something belongs to a singular noun, add apostrophe + s ('s):

• The cat's toy (the toy belonging to one cat)
• The phrase's simplicity (the simplicity belonging to one phrase)
• James's book (the book belonging to James)

2. Matching Pronouns to Their Antecedents:

A pronoun must agree in number with the noun it refers to (called the antecedent in grammar terms):

• Singular antecedent → singular pronoun (its, his, her)
  • The phrase is simple, but its complexity is hidden
• Plural antecedent → plural pronoun (their)
  • The phrases are simple, but their complexity is hidden

In this question:

• We need "phrase's" (singular possessive) because only one phrase is mentioned
• We need "its" (singular pronoun) to match the singular noun "phrase"
• Both elements must work together to maintain grammatical consistency