Gathering accurate data on water flow in the United States is challenging because of the country's millions of miles of...

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

• Gathering accurate data on water flow in the United States
  • is challenging
    • because of the country's millions of miles of waterways [?] the fact that
      • the volume and speed of water
        • at any given location
      • can vary drastically over time.
• Where [?] = deciding on punctuation around "and"

Understanding the Meaning

The sentence starts by telling us about a challenge:

• 'Gathering accurate data on water flow in the United States is challenging'
  • So collecting good information about water flow is difficult in the U.S.

Now let's see WHY it's challenging:

• 'because of the country's millions of miles of waterways...'

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

1. waterways and the fact that,
2. waterways, and the fact that,
3. waterways, and, the fact that
4. waterways and the fact that

The choices are asking us about comma placement around "and."

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

The sentence continues:

• 'the fact that the volume and speed of water at any given location can vary drastically over time.'

Now let's understand what this complete structure is telling us:

It's challenging because of TWO things:

• First reason: 'the country's millions of miles of waterways'
  • There's just SO MUCH water infrastructure to monitor - millions of miles of it

• Second reason: 'the fact that the volume and speed of water at any given location can vary drastically over time'
  • Even at one specific spot, the water conditions keep changing dramatically
  • This makes it even harder to get consistent, accurate measurements

What do we notice about the structure here?

• We have two noun phrases that both explain what it's challenging "because of"
  • Both phrases serve the same grammatical role (both objects of "because of")
  • They're connected by "and"

• The pattern is: "because of [thing 1] and [thing 2]"
  • waterways = thing 1
  • the fact that... = thing 2

When you have exactly two items joined by "and" like this, you don't use commas. The "and" does all the connecting work by itself.

So we need: D: waterways and the fact that (no commas)

GRAMMAR CONCEPT APPLIED

Comma Usage with Two Items Joined by "And"

When you have exactly two items of the same type connected by "and," you don't use commas around the "and." The conjunction connects them directly:

Pattern 1 - Two items (no commas):

• The store sells books and magazines
• Item 1: books
• Item 2: magazines
• Connected with: and (no commas)

Pattern 2 - Three or more items (commas needed):

• The store sells books, magazines, and newspapers
• Now we have three items, so we use commas

Pattern 3 - Two items with different structure (when items are independent clauses):

• The store sells books, and it offers free coffee
• These are two complete thoughts (independent clauses)
• Comma IS needed before "and"

In our question:

We have: "because of [noun phrase 1] and [noun phrase 2]"

• This follows Pattern 1 (two items that aren't complete sentences)
• So no commas are needed
• The structure is simply: waterways and the fact that...