Modern radio telescopes have revolutionized our understanding of distant cosmic phenomena. These sophisticated instruments _____ faint electromagnetic...

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

• Modern radio telescopes
  • have revolutionized our understanding of distant cosmic phenomena.
• These sophisticated instruments
  • [?] faint electromagnetic signals from galaxies billions of light-years away,
  • filter out interference from terrestrial sources, and
  • transmit processed data to research centers worldwide.

Understanding the Meaning

The first sentence gives us context:

• Modern radio telescopes have revolutionized our understanding of distant cosmic phenomena.
  • This sets up what we're talking about – these powerful telescopes that have changed how we understand the universe.

Now the second sentence starts telling us specifically what these instruments do:

• 'These sophisticated instruments...'
  • This refers back to the radio telescopes
  • 'These instruments' is PLURAL – we're talking about multiple telescopes

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

• 'These sophisticated instruments _____ faint electromagnetic signals from galaxies billions of light-years away...'

Let's look at our choices:

• A: detects (singular form)
• B: have detected (present perfect)
• C: detect (plural form)
• D: are detecting (progressive form)

What do we know so far?

• The subject is 'These sophisticated instruments' – which is PLURAL
• So we need a verb that works with a plural subject

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

• The sentence continues with a list of what these instruments do:
  • '_____ faint electromagnetic signals from galaxies billions of light-years away,'
  • 'filter out interference from terrestrial sources, and'
  • 'transmit processed data to research centers worldwide.'

What do we notice about the structure here?

• We have THREE actions listed in a series, all describing what these instruments do:
  • [blank] ... signals
  • filter out interference
  • transmit ... data
• Look at the second and third verbs: 'filter' and 'transmit'
  • Both are in the same form – simple present tense, plural
  • They're working together in parallel, like items in a list
• For the sentence to flow smoothly, the first verb needs to match this same pattern
  • It should also be simple present tense, plural form
• Plus, it needs to agree with the plural subject 'These sophisticated instruments'

So we need detect (Choice C) – it's the plural form that matches both the plural subject AND the parallel structure of 'filter' and 'transmit.'

GRAMMAR CONCEPT APPLIED

Matching Verb Forms in a Series (Parallel Structure) + Subject-Verb Agreement

This question tests two important grammar principles working together:

Principle 1: Subject-Verb Agreement
When your subject is plural, your verb must be in plural form:

• Singular: "This instrument detects signals"
• Plural: "These instruments detect signals"

Principle 2: Parallel Structure in a Series
When you list multiple verbs that all describe what the same subject does, they should be in the same form (called parallel structure in grammar terms):

Example 1:

• Correct: "The students read the book, discuss the themes, and write essays."
  • All three verbs are simple present tense
• Incorrect: "The students have read the book, discuss the themes, and write essays."
  • First verb is different form – breaks the parallel pattern

Example 2:

• Correct: "She analyzes data, identifies patterns, and creates reports."
  • All three verbs match in form

In our question:

• Subject: "These sophisticated instruments" (plural)
• Three verbs in series: "detect," "filter out," and "transmit"
• All three must be: (1) plural form to match the subject, and (2) same tense/form to maintain parallel structure
• Answer: "detect"