The research team analyzed climate patterns that—by examining ice cores and sediment ____—revealed temperature changes spanning over 800,000 years. Th...

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 research team analyzed climate patterns
• that—by examining ice cores and sediment layers[?]—revealed
  • temperature changes
  • spanning over 800,000 years.
• These findings confirmed predictions from atmospheric models.

Understanding the Meaning

• The sentence starts straightforward:
  • 'The research team analyzed climate patterns'
    • Scientists studied patterns in climate
• Then it tells us something about these patterns:
  • 'that—'
    • This dash signals an interruption is coming—extra information being inserted
• Now we get that interrupting information:
  • 'by examining ice cores and sediment layers'
    • This tells us HOW they analyzed these patterns—the method they used
• This is where we have the blank.
• Let's look at the choices:
  • A. layers,
  • B. layers:
  • C. layers—
  • D. layers
• We're deciding what punctuation (if any) should come after "layers."
• To see what works here, let's read the rest of the sentence and understand what it's saying!
• The sentence continues:
  • '—revealed temperature changes spanning over 800,000 years'
    • The patterns showed temperature changes across a huge time span
• What do we notice about the structure here?
  • The phrase 'by examining ice cores and sediment layers' is extra information inserted into the middle of the main sentence flow
  • If we remove that interrupting phrase, the core sentence reads:
    • 'The research team analyzed climate patterns that revealed temperature changes spanning over 800,000 years'
    • This works perfectly as a complete thought!
  • The interruption opens with a dash (—)
    • When you open an interruption with a dash, you must close it with a dash too
    • Dashes work in pairs to set off interrupting elements
• So we need C. layers— to complete the pair of dashes and properly close the interruption before the sentence returns to its main flow.

GRAMMAR CONCEPT APPLIED

Using Paired Dashes to Set Off Interrupting Elements

When you insert extra information in the middle of a sentence using dashes, you must use them in pairs—one to open the interruption and one to close it. The dashes signal "we're stepping away from the main sentence flow, and then we'll return to it."

The key test: The sentence should read smoothly if you remove everything between the dashes.

Example 1:

• With interruption: The scientist discovered—after years of searching—the missing data.
• Without interruption: The scientist discovered the missing data. ✓

Example 2:

• With interruption: The new policy, which took effect in May—will reduce costs significantly.
• Problem: Opens with comma but tries to close with dash ✗
• Correct: The new policy, which took effect in May, will reduce costs significantly. ✓
• Also correct: The new policy—which took effect in May—will reduce costs significantly. ✓

In this question:

• With interruption: Climate patterns that—by examining ice cores and sediment layers—revealed temperature changes
• Without interruption: Climate patterns that revealed temperature changes ✓
• The sentence flow is complete, confirming the dashes are properly paired