The marketing director analyzed consumer behavior across multiple platforms. She discovered that engagement rates varied significantly by ______ and h...

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 marketing director analyzed consumer behavior
• across multiple platforms.
• She discovered
• that engagement rates varied significantly by demographic[?]
• and her team identified three key factors
• influencing purchase decisions.

Understanding the Meaning

Let's start reading from the beginning:

The first sentence tells us:

• "The marketing director analyzed consumer behavior across multiple platforms"
  • She studied how consumers behave on different platforms (social media, websites, etc.)

Now the second sentence:

• "She discovered that engagement rates varied significantly by demographic"
  • She found out that different demographic groups (age groups, income levels, etc.) engage at very different rates

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

• We're deciding what punctuation (if any) should follow "demographic"
• Options are: nothing, comma, colon, or semicolon

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

• "and her team identified three key factors influencing purchase decisions"
  • This tells us another action - what her team did
  • They identified factors that influence whether people buy

What do we notice about the structure here?

• We have two complete thoughts being connected by "and":
  
  First complete thought:
  • "She discovered that engagement rates varied significantly by demographic"
    • Subject: She
    • Verb: discovered
    • This could stand alone as a sentence ✓
  
  Second complete thought:
  • "her team identified three key factors influencing purchase decisions"
    • Subject: her team
    • Verb: identified
    • This could also stand alone as a sentence ✓

• When we connect two complete thoughts with a connecting word like "and," we need a comma before the "and"
• This is the standard pattern: [complete thought], and [complete thought]

So we need a comma after "demographic" - before the word "and."

The correct answer is B: demographic,

GRAMMAR CONCEPT APPLIED

Connecting Two Complete Thoughts with "And"

When you want to combine two complete thoughts (each with its own subject and verb that could stand alone as a sentence) using a connecting word like "and," you need a comma before the "and." These connecting words are called coordinating conjunctions in grammar terms (and, but, or, nor, for, so, yet).

The pattern:

• [Complete thought], and [complete thought]

Examples:

• Two separate sentences:
  • The study revealed surprising results. The researchers published their findings immediately.

• Combined with comma + and:
  • The study revealed surprising results, and the researchers published their findings immediately.
    • First complete thought: "The study revealed surprising results" (subject = study, verb = revealed)
    • Second complete thought: "the researchers published their findings immediately" (subject = researchers, verb = published)
    • Comma before "and" connects them properly

In our question:

• First complete thought: "She discovered that engagement rates varied significantly by demographic"
• Second complete thought: "her team identified three key factors influencing purchase decisions"
• Proper connection: demographic, and her team...

Why the comma matters:

Without it, you create a run-on sentence - two complete thoughts improperly joined. The comma signals to the reader that one complete idea is ending and another is beginning, making the sentence structure clear and correct.