Carl Sagan revolutionized science communication through his television series Cosmos (1980), but he was equally devoted to planetary science, the...

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

• Carl Sagan revolutionized science communication
• through his television series Cosmos (1980),
• but he was equally devoted to planetary science,
• the study of celestial bodies [?]
• conducting groundbreaking research on Venus's atmospheric composition
• and leading NASA's efforts to send messages to extraterrestrial intelligence.

Where [?] represents:

1. bodies, conducting
2. bodies conducting
3. bodies; conducting
4. bodies. Conducting

Understanding the Meaning

Let's start reading from the beginning:

• Carl Sagan revolutionized science communication through his television series Cosmos (1980)
  • This tells us about Sagan's famous TV work
• But he was equally devoted to planetary science
  • Setting up a contrast - he wasn't just a TV personality, he was also a serious scientist
  • "planetary science" - the scientific study of planets and space
• "the study of celestial bodies"
  • This is defining what planetary science is - it's the study of celestial bodies (planets, moons, asteroids, etc.)

Now we reach the blank: "celestial bodies ____ conducting..."

Let's look at our choices - they're asking us what punctuation (if any) should come after "bodies" and before "conducting."

To understand what works here, let's read the rest of the sentence:

• "conducting groundbreaking research on Venus's atmospheric composition"
• "and leading NASA's efforts to send messages to extraterrestrial intelligence"

Now let's understand what these phrases are doing:

• "conducting groundbreaking research..." and "leading NASA's efforts..."
  • Both start with -ing words (conducting, leading)
  • These are telling us specific things that Carl Sagan DID
  • They're concrete examples of how he was "devoted to planetary science"
• These phrases are giving us additional information about Carl Sagan
  • They're describing his actions
  • They're showing us what his devotion to planetary science looked like in practice

What do we notice about the structure here?

• After defining planetary science as "the study of celestial bodies," the sentence continues by describing Carl Sagan's specific actions
• The phrases "conducting... and leading..." are additional descriptive elements that tell us what Carl Sagan did
• These -ing phrases need to be introduced - they're adding extra information to the main statement about his devotion to planetary science

Since these are additional descriptive phrases that continue the sentence and provide more information about Carl Sagan, they should be introduced with a comma.

The correct answer is A) bodies, conducting

The comma correctly separates the definition of planetary science from the additional descriptive phrases about what Carl Sagan actually did in this field.

GRAMMAR CONCEPT APPLIED

Using Commas with Additional Descriptive Phrases (Participial Phrases)

When you want to add extra information about someone's actions using phrases that start with -ing verbs (called participial phrases in grammar terms), you introduce these phrases with a comma:

Pattern:

• Main statement + comma + -ing phrase providing additional information

Example 1:

• The scientist made a breakthrough, discovering a new treatment for the disease
• Main statement: "The scientist made a breakthrough"
• Additional information: "discovering a new treatment" (tells us what the breakthrough was)
• Comma introduces the -ing phrase

Example 2:

• The author became famous, writing three bestselling novels in five years
• Main statement: "The author became famous"
• Additional information: "writing three bestselling novels" (tells us how they became famous)
• Comma introduces the -ing phrase

In our question:

• Main statement: "he was equally devoted to planetary science, the study of celestial bodies"
• Additional information: "conducting groundbreaking research... and leading NASA's efforts..."
• The comma after "bodies" introduces these -ing phrases that describe Carl Sagan's specific actions

The comma signals to the reader: "Here's more specific information about what this person did."