NASA has launched numerous Mars rovers over the past two decades to explore the planet's surface and search for signs...

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

• NASA has launched numerous Mars rovers
  • over the past two decades
  • to explore the planet's surface and search for signs of past life.

• The rover (?) named Perseverance
  • landed in Jezero Crater
    • in February 2021
  • and has since collected valuable geological samples.

Understanding the Meaning

The first sentence gives us context:

• NASA has launched numerous Mars rovers over the past two decades
  • So there have been MANY Mars rovers - not just one

• These rovers were sent to explore the planet's surface and search for signs of past life
  • This tells us the mission purpose

Now the second sentence focuses on one specific rover:

• 'The _____ Perseverance landed in Jezero Crater in February 2021'

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

• All four choices start with "rover"
• They differ in the punctuation (or lack of it) after "rover":
  • Choice A: rover (named
  • Choice B: rover, named
  • Choice C: rover—named
  • Choice D: rover named (no punctuation)

To see what works here, let's understand what "named Perseverance" is doing!

• We're talking about "the rover"
  • But WHICH rover? There have been many!

• "named Perseverance" tells us WHICH specific rover we're discussing
  • This isn't extra information - it's ESSENTIAL to identify the rover
  • Without "named Perseverance," we wouldn't know which of the many rovers landed in Jezero Crater

What do we notice about the structure here?

• "named Perseverance" is a modifier that's ESSENTIAL for identification
  • It's not bonus information that could be removed
  • It's necessary to understand which specific rover the sentence is about

• When a modifier is essential to identify what you're talking about, you DON'T use punctuation to separate it from the noun
  • The modifier stays directly attached to the noun

So we need: rover named (no punctuation)

The complete sentence tells us that this particular rover - the one named Perseverance - landed in Jezero Crater in February 2021 and has been collecting geological samples.

GRAMMAR CONCEPT APPLIED

Essential vs. Extra Information: When NOT to Use Punctuation

When a descriptive phrase is ESSENTIAL to identify which specific thing you're talking about, you don't use punctuation to separate it (this is called a restrictive modifier in grammar terms). When it's just EXTRA information about something already clearly identified, you DO use punctuation to set it off (called a non-restrictive modifier).

Pattern for ESSENTIAL information (no punctuation):

• Noun + Essential Identifier: The rover named Perseverance landed in 2021
• Without "named Perseverance," we wouldn't know WHICH rover
• The phrase is essential - no punctuation

• Another example: Students who study regularly perform better
• Without "who study regularly," we're talking about ALL students
• The phrase restricts which students - no punctuation

Pattern for EXTRA information (needs punctuation):

• Noun + Extra Detail: Mars, the fourth planet from the Sun, has fascinated scientists
• We already know which planet (Mars is clearly identified)
• "the fourth planet from the Sun" is bonus information - use commas

• Another example: Perseverance, which landed in 2021, is collecting samples
• We already know which rover (Perseverance is named)
• "which landed in 2021" adds extra information - use commas

How it applies here:

Since there are many Mars rovers and "named Perseverance" is ESSENTIAL to identify which specific rover we're discussing, no punctuation should separate "rover" from "named Perseverance."