A study showed that a solar park caused nearby land to cool, though the ecological impact of this temperature decrease...

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

Sentence 1:

• A study showed
  • that a solar park caused nearby land to cool,
    • though the ecological impact
      • of this temperature decrease
        • isn't yet known.

Sentence 2 (with blank):

• Before the park's construction,
  • the surface temperature
    • 30 meters outside of the park boundary
  • was 0.1°C cooler
    • than that of a control area [?] construction,
      • the temperature
        • 30 meters outside of the boundary
      • was 1.7°C cooler
        • than that of the control area.

Where [?] represents: area [punctuation?] after [punctuation?]

Understanding the Meaning

First, let's understand what the passage is telling us:

• The first sentence gives us context:
  • A study found that a solar park made nearby land cooler
  • Scientists don't yet know what this cooling means for the environment

Now the second sentence gives us specific measurements:

• "Before the park's construction, the surface temperature 30 meters outside of the park boundary was 0.1°C cooler than that of a control area"
  • Before they built the solar park
  • The temperature 30 meters away from where the park would be
  • Was just slightly cooler (0.1°C) than a control area

This is where we have the blank. Let's look at the choices:

• They're asking us how to punctuate around the word "after"
• We have: no punctuation, comma after "after," period before "After," or comma before "after"

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

• "after construction, the temperature 30 meters outside of the boundary was 1.7°C cooler than that of the control area"
  • After they built the solar park
  • The temperature at that same spot
  • Was much cooler (1.7°C) than the control area

So the complete picture is:

• We're comparing two time periods:
  • BEFORE construction → only 0.1°C cooler
  • AFTER construction → 1.7°C cooler
• The solar park made that spot significantly cooler!

Now, what do we notice about the structure here?

Let's look at the part BEFORE the blank:

• "Before the park's construction, the surface temperature 30 meters outside of the park boundary was 0.1°C cooler than that of a control area"
  • This is a complete thought with a subject and verb
  • It could stand alone as its own sentence

And the part AFTER the blank:

• "After construction, the temperature 30 meters outside of the boundary was 1.7°C cooler than that of the control area"
  • This is also a complete thought with a subject and verb
  • It could also stand alone as its own sentence

We have two complete sentences here! Two independent thoughts that each make sense on their own.

The rule is: You cannot join two complete sentences with just a comma (that's called a comma splice) or with no punctuation at all (that's a run-on sentence).

We need proper separation. The clearest way to separate two complete thoughts is with a period.

The correct answer is C: area. After

This creates two properly separated sentences, with "After" correctly capitalized to start the new sentence.

GRAMMAR CONCEPT APPLIED

Properly Separating Complete Sentences

When you have two complete thoughts (called independent clauses in grammar terms) - each with its own subject and verb that could stand alone as a sentence - you must separate them properly.

You CANNOT:

• Join them with no punctuation → run-on sentence
  • "The temperature was cooler the study confirmed this finding"
• Join them with only a comma → comma splice
  • "The temperature was cooler, the study confirmed this finding"

You MUST use one of these:

1. A period (two separate sentences):
   • "The temperature was cooler. The study confirmed this finding."
2. A semicolon:
   • "The temperature was cooler; the study confirmed this finding."
3. A comma + coordinating conjunction (and, but, or, nor, for, so, yet):
   • "The temperature was cooler, and the study confirmed this finding."

In our question:

• Part 1: "Before the park's construction, the surface temperature...was 0.1°C cooler than that of a control area" (complete sentence)
• Part 2: "After construction, the temperature...was 1.7°C cooler than that of the control area" (complete sentence)
• Solution: Use a period to create two separate sentences: "area. After"

This parallel structure (Before...After) actually emphasizes that these are distinct measurements, making two sentences the most logical and clear choice.