Before the Erie Canal was completed in 1825, transporting goods by wagon between New York City and the Midwest took...

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

• Before the Erie Canal was completed in 1825,
  • transporting goods by wagon
    • between New York City and the Midwest
  • took up to forty-five days
  • and cost one hundred dollars per ton.
• By linking the Hudson River to Lake Erie [?] the canal
  • reduced transport time to nine days
  • and cut costs to six dollars per ton.

Understanding the Meaning

The first sentence gives us the "before" picture:

• Before 1825, when the Erie Canal wasn't finished yet,
  • transporting goods by wagon between NYC and the Midwest
  • took 45 days and cost $100 per ton.

Now the second sentence shows us the dramatic improvement.

Let me read through it:

• 'By linking the Hudson River to Lake Erie'

This is where we have the blank.

Let's look at the choices:

1. Erie; the (semicolon)
2. Erie (the (open parenthesis)
3. Erie, the (comma)
4. Erie: the (colon)

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

• 'the canal reduced transport time to nine days and cut costs to six dollars per ton.'

Now let's understand what this is telling us:

• 'By linking the Hudson River to Lake Erie'
  • This describes HOW the canal achieved something
  • It's explaining the method - the canal connected these two bodies of water
• 'the canal reduced transport time to nine days and cut costs to six dollars per ton'
  • This is the main point of the sentence
  • This is WHAT the canal did - the actual accomplishment

What do we notice about the structure here?

• The sentence starts with a descriptive phrase
  • It sets up context by explaining HOW (by linking the two waterways)
• Then comes the main action
  • The canal reduced time and cut costs
• This is a pattern: an opening phrase that provides context, followed by the main statement

When a sentence begins with this kind of introductory phrase - one that sets the stage for the main action - we use a comma to separate it from the main part.

So we need Choice C: Erie, the (comma).

GRAMMAR CONCEPT APPLIED

Using Commas After Introductory Phrases

When you begin a sentence with a phrase that provides context - explaining when, where, how, or why something happened - you use a comma to separate that introductory element from the main part of the sentence (called the independent clause in grammar terms):

Pattern: Introductory phrase, main clause.

Example 1:

• Without context added: The company announced record profits.
• With introductory phrase: After years of struggling, the company announced record profits.
• "After years of struggling" = introductory phrase (when)
• Comma separates it from the main statement

Example 2:

• Main statement: Students performed better on tests.
• With introductory phrase: By studying in groups, students performed better on tests.
• "By studying in groups" = introductory phrase (how/method)
• Comma separates it from the main statement

In this question:

• Introductory phrase: "By linking the Hudson River to Lake Erie" (explains HOW)
• Comma needed here
• Main clause: "the canal reduced transport time to nine days and cut costs to six dollars per ton"

The comma signals to readers: "Here's the context/setup, and NOW here comes the main point."