Scientists developed a recycling method that, through chemical treatment and thermal ______ converts plastic waste into reusable materials. This innov...

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

• Scientists
  • developed a recycling method
    • that converts plastic waste into reusable materials
      • through chemical treatment and thermal processing[?]

• This innovation
  • has reduced landfill dependency
    • in several pilot programs.

Understanding the Meaning

Let's start reading from the beginning:

Scientists developed a recycling method –

• a new way to recycle materials.

The sentence tells us more about this method:

• 'that, through chemical treatment and thermal processing...'
  • We see there's a comma after 'that'
  • Then we get information about HOW the method works: through two processes (chemical treatment and thermal processing)

This is where we have the blank – right after 'processing.'

Let's look at the choices:

• A offers a comma
• B offers a colon
• C offers a dash
• D offers no punctuation

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

After the blank, the sentence continues:

• 'converts plastic waste into reusable materials'
  • This is what the method DOES – it converts plastic waste

So the complete picture is:

• The method converts plastic waste into reusable materials
• HOW does it convert? Through chemical treatment and thermal processing

Now, what do we notice about the structure here?

• 'Through chemical treatment and thermal processing' is extra information that interrupts the main flow
  • The base sentence would be: 'Scientists developed a recycling method that converts plastic waste'
  • We're inserting HOW it converts right in the middle

• This interrupting phrase has a comma BEFORE it (after 'that')
  • When you open an interruption with a comma, you need to close it with a comma too
  • This signals to the reader: 'OK, the extra information is done, now we're back to the main point'

So we need a comma after 'processing' to match the opening comma and complete the interruption.

The correct answer is Choice A: processing,

GRAMMAR CONCEPT APPLIED

Setting Off Interrupting Phrases with Commas

When you insert additional information in the middle of a sentence – information that interrupts the main flow – you need to set it off with matching punctuation on both sides. The most common pattern uses commas (this type of phrase is called a parenthetical element in grammar terms):

Pattern:

• Base sentence: Scientists developed a method that converts plastic waste
• Interrupting information added: through chemical treatment and thermal processing
• Complete sentence: Scientists developed a method that, through chemical treatment and thermal processing, converts plastic waste

Why matching punctuation matters:

• Opening comma (after "that") = signals "extra information is starting"
• Closing comma (after "processing") = signals "extra information is done, back to main point"
• Both commas work together like a pair of parentheses

Another example:

• Base: The study revealed surprising results
• With interruption: The study, conducted over five years, revealed surprising results
• Comma after "study" opens the interruption
• Comma after "years" closes the interruption

In this question:

The interrupting phrase "through chemical treatment and thermal processing" is inserted between "that" and "converts," so it needs commas on both sides to clearly mark where the interruption begins and ends.