Emperor penguins don't waddle out of the ocean. They launch themselves at such a high speed that they travel up...

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:

• Emperor penguins don't waddle out of the ocean.

Sentence 2:

• They launch themselves at such a high speed
  • that they travel up to two meters
    • before landing.

Sentence 3:

• How [? - are they/they are] able to move so fast [? - punctuation]
• A layer of microbubbles on their plumage
  • reduces friction
    • as the penguins speed to the surface.

Understanding the Meaning

Let's start from the beginning to understand what's happening:

• "Emperor penguins don't waddle out of the ocean."
  • So these penguins have a more dramatic exit than just waddling.

• "They launch themselves at such a high speed that they travel up to two meters before landing."
  • Wow! They're shooting out of the water and flying through the air for about 6 feet.
  • This is a pretty impressive feat.

Now we reach the blank: "How ______"

Let's look at our choices:

1. they are able to move so fast!
2. are they able to move so fast.
3. they are able to move so fast.
4. are they able to move so fast?

I'm deciding between:

• Word order: "they are" vs "are they"
• Punctuation: exclamation mark vs period vs question mark

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

The sentence continues: "A layer of microbubbles on their plumage reduces friction as the penguins speed to the surface."

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

• "How ______ able to move so fast"
  • This is introducing a QUESTION: How do they achieve this amazing speed?

• "A layer of microbubbles on their plumage reduces friction..."
  • This is providing the ANSWER to that question.
  • The microbubbles create a slippery surface that lets them zoom through the water.

So the structure is:

• Question posed → Answer provided

What do we notice about the structure here?

• When we start a sentence with "How" to ask a question, we need to flip the order:
  • NOT "they are" (regular statement order)
  • BUT "are they" (question order - the helping verb comes before the subject)

• This is an actual question being asked, so it needs:
  • The inverted word order: "are they"
  • A question mark at the end

So we need: "How are they able to move so fast?"

The correct answer is Choice D.

GRAMMAR CONCEPT APPLIED

Questions Starting with "How" and Other Question Words

When you start a question with a question word like "How," "Why," "When," or "Where," you need to use inverted word order (called subject-verb inversion in grammar terms). This means the helping verb comes before the subject:

Statement order (not a question):

• They are able to move fast.
  • Subject: "they"
  • Verb: "are"

Question order (interrogative):

• How are they able to move so fast?
  • Question word: "How"
  • Verb comes first: "are"
  • Then subject: "they"
  • Ends with question mark: "?"

More examples:

• Statement: You can see the difference.
• Question: Why can you see the difference?

• Statement: She will arrive tomorrow.
• Question: When will she arrive?

In this question:

• The passage poses a question: "How are they able to move so fast?"
• Then answers it: "A layer of microbubbles on their plumage reduces friction..."
• This rhetorical structure (question followed by answer) requires proper interrogative form with inverted word order and a question mark