The magnetar, source of powerful electromagnetic fields thousands of times stronger than typical neutron stars, _____ among the most extreme...

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

• The magnetar,
• source of powerful electromagnetic fields
  • thousands of times stronger than typical neutron stars,
• [? + comma]
• among the most extreme objects in the cosmos:
• some emit bursts of energy detectable across entire galaxies.

Understanding the Meaning

Let's start reading from the beginning.

The sentence introduces us to:

• 'The magnetar'
  • This is what the sentence is about - a specific type of astronomical object

Then we get descriptive information set off by commas:

• 'source of powerful electromagnetic fields thousands of times stronger than typical neutron stars'
  • This tells us what makes magnetars special
  • They produce incredibly powerful electromagnetic fields
  • Much stronger than regular neutron stars

Now here's where we need to fill in the blank:

• 'The magnetar _____ among the most extreme objects in the cosmos'

Let's look at our choices:

• They're all verb forms: are, is, have been, were
• They all have a comma after

What do we know so far?

• The subject is 'The magnetar' - that's singular
• The phrase about electromagnetic fields is just extra descriptive information set off by commas
• We need a verb that matches 'the magnetar'

So we need a singular verb: is,

The sentence is stating a general, current fact about magnetars, so present tense fits perfectly.

Now let's read the rest to see the complete picture:

• 'among the most extreme objects in the cosmos:'
  • This tells us the magnetar ranks among the most extreme objects

Then after a colon, we get a second sentence:

• 'some emit bursts of energy detectable across entire galaxies'
  • This gives us an example of WHY they're so extreme
  • Some magnetars send out energy bursts so powerful they can be detected across entire galaxies

What do we notice about the structure here?

• The true subject is 'The magnetar' (singular)
• The descriptive phrase between the commas separates the subject from its verb
• But that phrase doesn't change what the subject is
• We need to match the verb to 'the magnetar,' not to any of the words in the descriptive phrase

The correct answer is Choice B: is,

GRAMMAR CONCEPT APPLIED

Subject-Verb Agreement with Descriptive Phrases in Between

When a descriptive phrase set off by commas comes between your subject and verb, you need to 'look past' that phrase to identify the true subject and make sure your verb agrees with it:

Pattern:

• Subject (singular or plural)
• , descriptive information ,
• Verb (must match the subject's number)

Example 1:

• The scientist, along with her entire research team, is presenting today
• Subject: 'The scientist' (singular)
• Descriptive phrase: 'along with her entire research team'
• Verb: 'is' (singular, matching 'scientist')

Example 2:

• The students, each one carrying multiple textbooks, are heading to class
• Subject: 'The students' (plural)
• Descriptive phrase: 'each one carrying multiple textbooks'
• Verb: 'are' (plural, matching 'students')

In this question:

• Subject: 'The magnetar' (singular)
• Descriptive phrase: 'source of powerful electromagnetic fields thousands of times stronger than typical neutron stars'
• Verb needed: 'is' (singular, matching 'magnetar')

The key is to identify what the sentence is fundamentally about (the magnetar) and not get distracted by other nouns that appear in the descriptive phrase (like 'fields' or 'stars').