Marine biologist Dr. Sylvia Earle has dedicated her career to the exploration and protection of ocean ecosystems, documenting the impacts...

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

• Marine biologist Dr. Sylvia Earle
  • has dedicated her career
    • to the exploration and protection of ocean ecosystems,
  • documenting the impacts of (?) pollution, overfishing, and climate change
    • on marine biodiversity
    • through hundreds of underwater expeditions.

Where (?):

• Choice A: : (colon)
• Choice B: — (dash)
• Choice C: , (comma)
• Choice D: nothing

Understanding the Meaning

Let's start reading from the beginning:

• "Marine biologist Dr. Sylvia Earle has dedicated her career to the exploration and protection of ocean ecosystems,"
  • So Dr. Earle has devoted her professional life to exploring and protecting ocean ecosystems.

Now the sentence continues with another action:

• "documenting the impacts of (?) pollution, overfishing, and climate change on marine biodiversity through hundreds of underwater expeditions."

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

• They're asking us whether to put a colon, dash, comma, or no punctuation after "of."

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

• "documenting the impacts of [?] pollution, overfishing, and climate change on marine biodiversity through hundreds of underwater expeditions."

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

• "the impacts of"
  • "impacts" is a noun
  • "of" is introducing what causes those impacts
• "pollution, overfishing, and climate change"
  • These are the three things that create impacts
  • They form a list of items
• "on marine biodiversity"
  • This tells us what is affected by these impacts
• "through hundreds of underwater expeditions"
  • This tells us how Dr. Earle has been documenting these impacts

What do we notice about the structure here?

• We have the phrase "the impacts of pollution, overfishing, and climate change"
  • "of" connects directly to the list that follows it
  • The structure is: noun + of + list of things
• This is like saying "the benefits of exercise" or "the effects of climate"
  • The word "of" introduces what comes next
  • It needs to connect directly - no pause, no interruption
• The list itself has commas to separate the items (pollution, overfishing, and climate change)
  • But there should be nothing between "of" and the first item in the list
  • The connection from "of" to "pollution" needs to be direct

So we need Choice D: of (with no punctuation). The word "of" flows directly into what it's introducing without any interruption.

GRAMMAR CONCEPT APPLIED

Prepositions Connect Directly to What Follows

When you use a preposition—a word like "of," "in," "at," "to," "from," "with"—it needs to connect directly to what comes after it without any punctuation in between. The preposition and its object (the word or phrase that follows) form a grammatical unit that shouldn't be interrupted.

The pattern:

• Preposition + Object: the benefits of exercise
  • "of" connects directly to "exercise"
  • No punctuation between them
• Preposition + List: a story about courage, loss, and hope
  • "about" connects directly to the first item
  • The list items are separated by commas, but nothing comes between "about" and "courage"

In this question:

• Phrase: the impacts of pollution, overfishing, and climate change
  • "of" connects directly to "pollution" (the first item)
  • The three items in the list are separated by commas
  • But "of" itself needs no punctuation after it

Why this matters:

The preposition "of" is doing a job—it's introducing the things that create impacts. If you put punctuation right after "of," you interrupt that job and break the natural grammatical connection. The phrase "impacts of" is incomplete without what follows, so they need to connect smoothly without interruption.