After years of searching the deep Pacific Ocean, marine biologist Dr. Elena Martinez finally located the wreck of a Spanish...

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

Sentence 1:

• After years of searching the deep Pacific Ocean,
• marine biologist Dr. Elena Martinez finally located the wreck of a Spanish galleon that had been missing since 1715.

Sentence 2:

• The discovery was made at a depth of nearly 3,000 feet [?] according to maritime experts,
• the finding could reveal important information about colonial-era trade routes.

Where [?] = "and" / ". A" / "," / ""

Understanding the Meaning

Let's start from the beginning:

The first sentence tells us:

• After years of searching the Pacific Ocean, Dr. Elena Martinez found a Spanish shipwreck that had been missing since 1715.
  • This gives us the background and main discovery.

Now the second sentence begins:

• "The discovery was made at a depth of nearly 3,000 feet..."
  • This tells us where the wreck was found - how deep underwater.

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

• Choice A: "feet and according"
• Choice B: "feet. According" (period, capital A)
• Choice C: "feet, according"
• Choice D: "feet according"

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

The sentence continues:

• "according to maritime experts, the finding could reveal important information about colonial-era trade routes."
  • "According to maritime experts" tells us the source of the following information
  • "the finding could reveal important information..." is what the experts are saying

Now let's understand what we have structurally:

Part 1: "The discovery was made at a depth of nearly 3,000 feet"

• This is a complete thought
  • Subject: "The discovery"
  • Verb: "was made"
  • It tells us something complete - where the discovery happened

Part 2: "according to maritime experts, the finding could reveal important information about colonial-era trade routes"

• This is also a complete thought
  • Subject: "the finding"
  • Verb: "could reveal"
  • It expresses a complete idea - what the experts think about the finding

What do we notice about the structure here?

• We have TWO complete sentences - two complete thoughts that could each stand on their own
  • The first tells us the depth where the discovery was made
  • The second tells us what experts think this finding means
• When you have two complete sentences, they need proper separation
  • They can't just run together with no punctuation (that's a run-on)
  • They can't be joined with just a comma (that's a comma splice)
  • They need a period to end one sentence and start the next

So we need: feet. According (Choice B)

The period ends the first complete sentence about the depth, and "According" is capitalized because it starts a new sentence.

GRAMMAR CONCEPT APPLIED

Separating Complete Sentences (Independent Clauses)

When you have two complete thoughts that could each stand alone as sentences (called independent clauses in grammar terms), you must separate them properly. You have several options:

Option 1: Use a period

• First complete sentence.
• Second complete sentence.
• Example: "The discovery was made at a depth of nearly 3,000 feet. According to maritime experts, the finding could reveal important information."

Option 2: Use a semicolon

• First complete sentence; second complete sentence.
• Example: "The wreck was found at great depth; the finding excited researchers."

Option 3: Use a comma + coordinating conjunction (and, but, or, nor, for, yet, so)

• First complete sentence, and second complete sentence.
• Example: "The discovery was made at great depth, and it could reveal important information."

What you CANNOT do:

• Use just a comma (creates a comma splice)
• Use no punctuation (creates a run-on/fused sentence)
• Use a coordinating conjunction without proper setup

In this question, we have two distinct complete thoughts that work best as separate sentences, so we need the period to separate them clearly.