Researcher Lin Zhi developed a process for increasing the tensile strength—measured in gigapascals, or GPa—of silkworm ______ dissolving and reweaving...

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

• Researcher Lin Zhi
  • developed a process
    • for increasing the tensile strength
      • —measured in gigapascals, or GPa—
      • of silkworm silk [?]
• dissolving and reweaving the silk
  • in a solution of iron metal ions, zinc, and sugar,
  • Zhi increased the amount of force required to stretch it
    • from approximately \(0.5\) GPa to \(2\) GPa.

Understanding the Meaning

Let's start by reading from the beginning:

'Researcher Lin Zhi developed a process for increasing the tensile strength—measured in gigapascals, or GPa—of silkworm silk'

Breaking this down:

• Lin Zhi (a researcher) developed a process
  • The process was for making silkworm silk stronger
  • Tensile strength = how much force something can handle when stretched
  • This strength is measured in gigapascals (GPa)

This is where we have the blank. Let's look at the choices - they're asking us whether to use a comma, no punctuation, "and," or a period before the word "by."

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

'dissolving and reweaving the silk in a solution of iron metal ions, zinc, and sugar, Zhi increased the amount of force required to stretch it from approximately \(0.5\) GPa to \(2\) GPa.'

Now let's understand what this is telling us:

• 'By dissolving and reweaving the silk in a solution of iron metal ions, zinc, and sugar'
  • This describes HOW the process worked
  • Zhi dissolved the silk and rewove it in a special solution

• 'Zhi increased the amount of force required to stretch it from approximately \(0.5\) GPa to \(2\) GPa'
  • This tells us the RESULT
  • The silk became much stronger - it went from withstanding \(0.5\) GPa to \(2\) GPa
  • That's four times stronger!

So the complete picture is:

• The first part tells us Lin Zhi developed a process to make silk stronger
• The second part tells us what that process was (dissolving and reweaving) and what it accomplished (made the silk 4x stronger)

What do we notice about the structure here?

• The first part is a complete sentence:
  • "Researcher Lin Zhi developed a process for increasing the tensile strength of silkworm silk."
  • It has a subject (Lin Zhi), a verb (developed), and expresses a complete thought

• The second part is ALSO a complete sentence:
  • "By dissolving and reweaving the silk in a solution of iron metal ions, zinc, and sugar, Zhi increased the amount of force required to stretch it from approximately \(0.5\) GPa to \(2\) GPa."
  • It has a subject (Zhi), a verb (increased), and expresses a complete thought

• We have TWO complete thoughts here - two sentences that could each stand alone

When you have two complete sentences, you need to separate them properly. You can't just use a comma or run them together - that creates errors. You need strong punctuation like a period.

The correct answer is D (silk. By) - this properly separates the two complete sentences with a period, and starts the new sentence with a capital "B."

GRAMMAR CONCEPT APPLIED

Recognizing When Two Complete Thoughts Need Separation

When you have two independent clauses (called this in grammar terms because they can stand independently as sentences), you must separate them properly. Each independent clause has:

• A subject
• A verb
• A complete thought

How to properly separate two independent clauses:

1. Use a period (make them separate sentences):
   • The experiment succeeded. The results were published immediately.
2. Use a semicolon:
   • The experiment succeeded; the results were published immediately.
3. Use a comma + coordinating conjunction (and, but, or, nor, for, yet, so):
   • The experiment succeeded, and the results were published immediately.

What you CANNOT do:

Comma splice (comma only): The experiment succeeded, the results were published immediately.

Run-on (no punctuation): The experiment succeeded the results were published immediately.

In our question:

• First independent clause: "Researcher Lin Zhi developed a process for increasing the tensile strength of silkworm silk"
• Second independent clause: "By dissolving and reweaving the silk in a solution of iron metal ions, zinc, and sugar, Zhi increased the amount of force required to stretch it from approximately \(0.5\) GPa to \(2\) GPa"
• Solution: Use a period to make them two separate sentences → "silk. By"