When researchers tracked the movement patterns of arctic foxes across northern Canada over three decades, they documented a northward range...

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

• When researchers tracked the movement patterns of arctic foxes
  • across northern Canada
  • over three decades,
• they documented a northward range shift
  • of approximately forty miles [?]

• [?] shifts often indicate climate adaptation:
  • as temperatures rise,
  • species migrate toward cooler latitudes
    • to maintain their optimal thermal range.

Understanding the Meaning

Let's read from the beginning to understand what this passage is telling us:

"When researchers tracked the movement patterns of arctic foxes across northern Canada over three decades"

• This sets up the research - scientists studying where arctic foxes moved over a 30-year period in northern Canada.

"they documented a northward range shift of approximately forty miles"

• Here's what they found: the foxes moved about forty miles north.

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

• A: miles, these (comma, lowercase)
• B: miles. These (period, capital)
• C: miles and these (conjunction, lowercase)
• D: miles these (no punctuation, lowercase)

So we're deciding on the punctuation between "miles" and what comes next.

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

"These shifts often indicate climate adaptation: as temperatures rise, species migrate toward cooler latitudes to maintain their optimal thermal range."

Now let's understand what this part is telling us:

• "These shifts" refers back to range shifts like the one just mentioned
• "often indicate climate adaptation" - these movements show how species adapt to climate
• The part after the colon explains HOW:
  • When it gets warmer, species move toward cooler areas (higher latitudes)
  • This helps them stay in temperatures they're adapted to

So the complete picture is:

• First part: Researchers found arctic foxes moved 40 miles north
• Second part: Such movements generally show climate adaptation - species moving to maintain comfortable temperatures

What do we notice about the structure here?

The first part - "When researchers tracked...forty miles" - is a complete thought:

• It has a subject: "they" (the researchers)
• It has a main verb: "documented"
• It expresses a complete idea that could stand alone as a sentence

The second part - "These shifts often indicate..." - is ALSO a complete thought:

• It has its own subject: "These shifts"
• It has its own main verb: "indicate"
• It also expresses a complete idea that could stand alone

So we have TWO COMPLETE SENTENCES here.

When you have two complete sentences, they need to be properly separated:

• You can use a period to separate them
• You can use a semicolon
• You can use a comma + a coordinating conjunction (like "and," "but," "so")

What you CANNOT do:

• Connect them with just a comma (this creates an error)
• Run them together with no punctuation (this also creates an error)

The correct answer is B: miles. These

This properly separates the two complete sentences with a period, and "These" is correctly capitalized as the start of a new sentence.

GRAMMAR CONCEPT APPLIED

Separating Complete Sentences (Independent Clauses)

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

Three correct ways to handle two independent clauses:

1. Period (Full Stop)
   • First complete sentence. Second complete sentence.
   • Example: "The study lasted three decades. The results were surprising."
2. Semicolon
   • First complete sentence; second complete sentence.
   • Example: "The study lasted three decades; the results were surprising."
3. Comma + Coordinating Conjunction
   • First complete sentence, and/but/so/etc. second complete sentence.
   • Example: "The study lasted three decades, and the results were surprising."

Two common errors to avoid:

1. Comma Splice - using only a comma
   • "The study lasted three decades, the results were surprising."
   • This is incorrect because a comma alone cannot connect two complete sentences
2. Run-on Sentence - using no punctuation
   • "The study lasted three decades the results were surprising."
   • This is incorrect because complete sentences need separation

In this question:

• Part 1: "When researchers tracked...forty miles" = complete sentence
• Part 2: "These shifts often indicate..." = complete sentence
• Solution: Period separates them correctly → "miles. These"