The microscope revolutionized scientific observation when it was invented in the late 16th century. Its impact on biological research was...

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 microscope revolutionized scientific observation
• when it was invented in the late 16th century.
• Its impact on biological research was immediate and profound [?]
• some scientists could finally observe individual cells,
• others discovered previously invisible microorganisms.

Understanding the Meaning

Let's start from the beginning:

The first sentence tells us:

• 'The microscope revolutionized scientific observation when it was invented in the late 16th century.'
  • This gives us the historical context - the microscope was a game-changer for science.

Now the second sentence begins:

• 'Its impact on biological research was immediate and profound'
  • This is talking about how the microscope affected biology specifically
  • The impact was both immediate (happened right away) and profound (deeply significant)

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

• A: profound, while
• B: profound:
• C: profound while
• D: profound,

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

The sentence continues:

• 'some scientists could finally observe individual cells, others discovered previously invisible microorganisms'
  • This gives us specific examples of what scientists could now do
  • Some could see individual cells for the first time
  • Others found tiny organisms that had been invisible before

What do we notice about the structure here?

• The first part 'Its impact...was immediate and profound' is a complete sentence that makes a general statement
• The second part gives us the SPECIFICS - it shows us exactly what that 'profound' impact looked like in concrete terms
  • It's not contrasting with the first part
  • It's EXPLAINING the first part - showing us what 'profound' means by giving real examples
• This is a classic case where we need a colon
  • A colon says: "Here's what I mean by that" or "Let me show you the details"
  • It introduces an explanation or elaboration of what came before

So we need a colon after 'profound' to introduce these specific examples that explain what the profound impact was.

The correct answer is B: profound:

GRAMMAR CONCEPT APPLIED

Using a Colon to Introduce Explanations or Examples

When you have a complete sentence that makes a general statement, and you want to follow it with specific details, examples, or an explanation of that statement, use a colon to connect them. The colon signals to the reader: "Here come the specifics" or "Let me show you what I mean."

The pattern:

• Complete sentence (general statement) + colon + explanation/examples/elaboration

Examples:

Example 1:

• General statement: The microscope had three major impacts
• With colon and specifics: The microscope had three major impacts: it revealed cellular structure, it discovered microorganisms, and it transformed medical understanding

Example 2:

• General statement: The discovery was unprecedented
• With colon and explanation: The discovery was unprecedented: never before had scientists observed living cells in such detail

In our question:

• General statement: "Its impact on biological research was immediate and profound"
• Colon introduces: specific examples of what that profound impact looked like (observing cells, discovering microorganisms)

The colon creates a clear relationship: the second part elaborates on or explains the first part.