While light is known as one of the fastest-moving substances, it slows down when passing through some types of matter....

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

• While light is known as one of the fastest-moving substances,
  • it slows down
    • when passing through some types of matter.

• One such type of matter is a form of cooled, condensed gas
  • called a Bose-Einstein condensate (BEC)[?]
• Dutch physicist Lene Hau famously used a BEC
  • to slow a beam of light
    • to a complete halt.

• Where [?] = comma / "and" / semicolon / nothing

Understanding the Meaning

Let's start from the beginning:

The first sentence gives us some background:

• "While light is known as one of the fastest-moving substances, it slows down when passing through some types of matter."
  • So light is super fast, but certain materials can slow it down.

Now the passage gets more specific:

• "One such type of matter is a form of cooled, condensed gas called a Bose-Einstein condensate (BEC)"
  • This tells us about one specific type of matter that slows light
  • It's a special kind of cooled gas
  • It's called a Bose-Einstein condensate, or BEC for short

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

• We need to decide whether to use a comma, "and", a semicolon, or nothing

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

The text continues:

• "Dutch physicist Lene Hau famously used a BEC to slow a beam of light to a complete halt."
  • This gives us a real-world example
  • A physicist named Lene Hau actually used one of these BECs
  • She managed to completely stop light with it

Now, what do we notice about the structure here?

Let me look at what comes before and after the blank:

• Before the blank: "One such type of matter is a form of cooled, condensed gas called a Bose-Einstein condensate (BEC)"
  • This is a complete thought that could stand alone
  • It has a subject ("One such type of matter") and a verb ("is")
  • It tells us everything we need to know: what this type of matter is

• After the blank: "Dutch physicist Lene Hau famously used a BEC to slow a beam of light to a complete halt."
  • This is also a complete thought that could stand alone
  • It has a subject ("Dutch physicist Lene Hau") and a verb ("used")
  • It gives us a complete example of how a BEC was used

So we have two complete sentences that are closely related in meaning—the second one provides a specific example to illustrate the first.

When you have two complete sentences that are closely related, you need strong enough punctuation to properly separate them. A semicolon does exactly this job.

The correct answer is C: (BEC);

The semicolon joins these two complete, closely related thoughts while maintaining the proper separation between them.

GRAMMAR CONCEPT APPLIED

Joining Two Complete Sentences with a Semicolon

When you have two complete sentences (each with its own subject and verb, expressing a complete thought—called independent clauses in grammar terms) that are closely related in meaning, you have several options for punctuation:

Option 1: Separate with a period

• Sentence one. Sentence two.
• Most straightforward, but can feel choppy if overused

Option 2: Join with a semicolon

• Sentence one; sentence two.
• Use this when the two thoughts are closely connected
• The semicolon says: "These are separate complete thoughts, but they're closely related"

Option 3: Join with comma + coordinating conjunction

• Sentence one, and sentence two.
• Must have BOTH the comma AND the conjunction (and, but, or, for, nor, yet, so)

In this question:

• First complete sentence: "One such type of matter is a form of cooled, condensed gas called a Bose-Einstein condensate (BEC)"
  • Subject: "One such type of matter"
  • Verb: "is"
  • Complete thought: tells us what this type of matter is

• Second complete sentence: "Dutch physicist Lene Hau famously used a BEC to slow a beam of light to a complete halt"
  • Subject: "Dutch physicist Lene Hau"
  • Verb: "used"
  • Complete thought: tells us who used a BEC and what they accomplished

• These sentences are closely related (the second provides a specific example of the first)
• A semicolon perfectly joins them while maintaining proper separation