The Hubble Space Telescope captured images of galaxies over thirteen billion light-years _____ structures from merely five hundred million years...

Sentence Structure

• The Hubble Space Telescope
  • captured images
    • of galaxies
      • over thirteen billion light-years away [?] revealing structures
        • from merely five hundred million years
          • after the Big Bang.

Where [?] represents what we need to decide:

• A: . R (period + new sentence)
• B: and r (conjunction)
• C: (nothing)
• D: , r (comma)

Understanding the Meaning

Let's start reading from the beginning:

"The Hubble Space Telescope captured images of galaxies over thirteen billion light-years away"

So we're learning that:

• The Hubble telescope captured some images
• These images were of galaxies
• Those galaxies are incredibly far away - over 13 billion light-years from us

This is where we have the blank.

Let's look at the choices:

• We're deciding what punctuation or connection to use before "revealing"
• Options are: period and new sentence, "and," nothing, or a comma

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

The sentence continues: "revealing structures from merely five hundred million years after the Big Bang."

Now let's understand what this is telling us:

• "Revealing structures"
  • The images revealed or showed certain structures
• "From merely five hundred million years after the Big Bang"
  • These structures date back to a very early time in the universe
  • Just 500 million years after the Big Bang (which is incredibly early in cosmic terms)

So the complete picture is:

• The telescope captured images of distant galaxies
• Those images revealed ancient structures from the early universe

What do we notice about the structure here?

• The first part - "The Hubble Space Telescope captured images of galaxies over thirteen billion light-years away" - is a complete thought
  • It has a subject (telescope) and verb (captured)
  • It can stand on its own as a sentence
• The second part - "revealing structures from merely five hundred million years after the Big Bang" - is NOT a complete thought
  • It doesn't have its own subject
  • It's a descriptive phrase that tells us what those images did
  • It adds extra information about the result or accomplishment of capturing those images

When we have a complete statement followed by a descriptive phrase that adds information (using an -ing verb form like "revealing"), we need a comma to set off that descriptive phrase.

The comma signals: "Here's some additional descriptive information about what I just told you."

So we need: Choice D - a comma before "revealing"

GRAMMAR CONCEPT APPLIED

Using Commas with Descriptive -ing Phrases

When you add a descriptive phrase to the end of a complete statement, and that phrase starts with an -ing verb form (called a present participle in grammar terms) that provides additional information, you need to set it off with a comma.

The pattern:

[Complete statement], [verb-ing phrase that adds information]

Examples:

Example 1:

• Complete statement: The researchers analyzed the data for months
• Adding descriptive phrase: The researchers analyzed the data for months, discovering patterns no one had noticed before
• "discovering patterns..." tells us what resulted from analyzing the data

Example 2:

• Complete statement: The artist completed the mural in three weeks
• Adding descriptive phrase: The artist completed the mural in three weeks, using only recycled materials
• "using only recycled materials" gives us additional information about how the work was done

In our question:

• Complete statement: The Hubble Space Telescope captured images of galaxies over thirteen billion light-years away
• Descriptive phrase added: revealing structures from merely five hundred million years after the Big Bang
• Result: The Hubble Space Telescope captured images of galaxies over thirteen billion light-years away, revealing structures from merely five hundred million years after the Big Bang

The comma is essential because it signals that what follows is extra descriptive information about the main action, not a separate complete thought.