The spacecraft launched by NASA over the past decade have revolutionized our understanding of distant planets. Working with aerospace engineers,...

Sentence Structure

• First sentence:
  • The spacecraft launched by NASA over the past decade
    • have revolutionized our understanding of distant planets.
• Second sentence:
  • Working with aerospace engineers,
  • the agency
    • refined the design of a new capsule prototype,
    • reinforcing its heat shield and
    • making (?) more aerodynamic for atmospheric reentry.

Understanding the Meaning

The first sentence gives us context:

• "The spacecraft launched by NASA over the past decade have revolutionized our understanding of distant planets."
  • This sets the scene about NASA's spacecraft work, but it's complete background.

Now let's look at the second sentence:

• "Working with aerospace engineers, the agency refined the design of a new capsule prototype"
  • NASA worked with engineers to improve a specific capsule design
  • Note: "a new capsule prototype" - this is singular, one prototype

The sentence continues with two things they did to this prototype:

• "reinforcing its heat shield"
  • They made the heat shield stronger
  • Notice "its" - referring to the prototype (singular)

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

• "and making _____ more aerodynamic for atmospheric reentry"

Let's look at our choices:

• A. them (plural)
• B. it (singular)
• C. those (plural)
• D. one (singular, but more formal)

What do we notice about the reference here?

• We need a word that refers back to "a new capsule prototype"
• The prototype is singular (a capsule, not capsules)
• The sentence already used "its" to refer to this same prototype
• So we need another singular pronoun to maintain consistency

The correct answer is it - matching the singular "prototype" and staying consistent with "its" used earlier in the same sentence.

GRAMMAR CONCEPT APPLIED

Pronoun Agreement: Making Sure Pronouns Match Their Antecedents

When a pronoun refers back to a noun mentioned earlier (called the antecedent in grammar terms), it must match that noun in number - singular with singular, plural with plural.

Here's how this works:

Pattern 1: Singular antecedent → singular pronoun

• The company announced its expansion plans and said it would hire 500 workers.
• Antecedent: "the company" (singular)
• Pronouns: "its" and "it" (both singular)

Pattern 2: Plural antecedent → plural pronoun

• The companies announced their merger and said they would combine operations.
• Antecedent: "the companies" (plural)
• Pronouns: "their" and "they" (both plural)

In this question:

• Antecedent: "a new capsule prototype" (singular - it's one prototype)
• First pronoun: "its" heat shield (singular possessive)
• Second pronoun: making "it" more aerodynamic (singular)
• Both pronouns must be singular to match the singular antecedent

Key tip: Look for clues! If the sentence has already used one pronoun to refer to something (like "its" in this question), other pronouns referring to that same thing should match in number.