British scientists James Watson and Francis Crick won the Nobel Prize in part for their 1953 paper announcing the double...

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

• British scientists James Watson and Francis Crick
  • won the Nobel Prize in part for their 1953 paper
    • announcing the double helix structure of DNA,
  • but it is misleading to say that Watson and Crick discovered the double helix.

• (?) findings
  • were based on a famous X-ray image of DNA fibers,
    • 'Photo 51,'
      • developed by X-ray crystallographer
        • Rosalind Franklin
          • and her graduate student
            • Raymond Gosling.

Understanding the Meaning

The first sentence tells us about Watson and Crick:

• British scientists James Watson and Francis Crick won the Nobel Prize
  • They won it for a 1953 paper about the double helix structure of DNA

But then we get an important correction:

• It is misleading to say that Watson and Crick discovered the double helix
  • So even though they got the Nobel Prize, calling it their "discovery" isn't quite right

This is where we have the blank. The second sentence continues:

• "______ findings were based on a famous X-ray image..."

Let's look at our choices:

• They're vs. It's (contractions meaning "they are" and "it is")
• Their vs. Its (possessive forms showing ownership - plural and singular)

To see what works here, let's read the rest of the sentence and understand what it's saying!

The sentence tells us about these findings:

• They were based on a famous X-ray image of DNA fibers
  • This image was called 'Photo 51'
  • Photo 51 was developed by Rosalind Franklin (an X-ray crystallographer) and Raymond Gosling (her graduate student)

So the complete picture is:

• Watson and Crick's work was actually based on Franklin and Gosling's X-ray image
• That's why it's misleading to say Watson and Crick "discovered" the double helix - they were building on someone else's work

What do we notice about the structure here?

We need to fill in: "______ findings were based on..."

• This is asking WHOSE findings we're talking about
• To show ownership, we need a possessive form, not a contraction
  • This eliminates "They're" and "It's" (those are verb contractions)

Between "Their" and "Its":

• We need to look back at who had these findings
• The previous sentence discussed "Watson and Crick" - that's two people
• Two people = plural
• So we need the plural possessive: Their

The correct answer is C. Their - it's possessive (showing these are Watson and Crick's findings) and plural (matching the two people we're referring to).

GRAMMAR CONCEPT APPLIED

Possessive Pronouns and Pronoun-Antecedent Agreement

When you need to show ownership or possession, you must:

1. Use the possessive form, not a contraction:
   • Possessive forms: their, its, your, whose (show ownership)
   • Contractions: they're (they are), it's (it is), you're (you are), who's (who is)
   • Example: "The scientists published their findings" (not "they're findings")
2. Match the number of your antecedent (the word the pronoun refers back to):
   • Plural antecedent → their
     • "Watson and Crick published their paper"
     • Antecedent: Watson and Crick (two people = plural)
     • Pronoun: their (plural possessive)
   • Singular antecedent → its
     • "The company published its earnings report"
     • Antecedent: The company (one entity = singular)
     • Pronoun: its (singular possessive)

In this question:

• We need possessive to show whose findings (eliminates They're/It's)
• The antecedent is "Watson and Crick" = two people = plural
• Therefore, we need "Their" (plural possessive)

Quick memory trick: If you can substitute "they are" or "it is," then you need the contraction (they're/it's). If you can't make that substitution, you need the possessive form (their/its).