Archaeologists have estimated that the pre-Columbian Native American city of Cahokia, located across the Mississippi River from modern-day St. Louis,...

Sentence Structure

• Archaeologists have estimated
  • that the pre-Columbian Native American city of Cahokia,
    • located across the Mississippi River
      • from modern-day St. Louis, Missouri,
  • had as many as 20,000 inhabitants in the year 1150 CE (?) making
    • it one of the largest cities
      • in North America
      • at the time.

Understanding the Meaning

Let's start reading from the beginning to understand what this sentence is telling us:

Archaeologists have estimated that the pre-Columbian Native American city of Cahokia had as many as 20,000 inhabitants in the year 1150 CE.

So we're learning about:

• Cahokia – a Native American city that existed before Columbus arrived
  • Located across the Mississippi River from modern-day St. Louis
• What archaeologists discovered: this city had about 20,000 people living in it in 1150 CE

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

• A. CE making (no punctuation)
• B. CE. Making (period, capital M)
• C. CE, making (comma)
• D. CE; making (semicolon)

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

The sentence continues: "making it one of the largest cities in North America at the time."

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

• "Making it one of the largest cities in North America at the time"
  • This is explaining what that population of 20,000 meant
  • It's telling us the significance – that this population size made Cahokia one of the largest cities around

What do we notice about the structure here?

• We have a complete thought first:
  • "Archaeologists have estimated that... Cahokia had as many as 20,000 inhabitants in 1150 CE"
  • This could stand alone as a sentence – it expresses a complete idea
• Then we have additional descriptive information:
  • "making it one of the largest cities in North America at the time"
  • This part CANNOT stand alone – it's describing the result or consequence of what we just learned
  • It's adding extra information about what that population figure meant
• This is a pattern where we have: complete statement + descriptive phrase that adds related information

When we have a complete thought followed by a descriptive phrase like this (starting with an "-ing" word that describes a result or adds information), we use a comma to connect them.

The correct answer is C: CE, making

GRAMMAR CONCEPT APPLIED

Using Commas with Descriptive "-ing" Phrases

When you have a complete thought followed by a phrase that starts with an "-ing" verb form (called a participial phrase in grammar terms) that adds descriptive information, consequence, or result, use a comma to connect them:

Pattern:

• Complete statement, + descriptive "-ing" phrase

Example 1:

• The storm knocked out power to 50,000 homes, leaving residents without electricity for three days.
• "The storm knocked out power to 50,000 homes" = complete thought
• "leaving residents without electricity for three days" = descriptive phrase showing the result

Example 2:

• Scientists discovered a new species of frog in the Amazon, bringing the total number of known species to over 7,000.
• First part = complete statement
• "bringing the total..." = phrase describing the consequence of the discovery

In our question:

• "Archaeologists have estimated that... Cahokia had as many as 20,000 inhabitants in 1150 CE" = complete thought
• "making it one of the largest cities in North America at the time" = descriptive phrase showing what that population meant
• The comma correctly connects these two parts