Recent studies of coral reefs have revealed that certain species can adapt to warming ocean temperatures more rapidly than scientists...

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

• Recent studies of coral reefs
  • have revealed that certain species can adapt to warming ocean temperatures
    • more rapidly than scientists initially predicted.

• This phenomenon is termed thermal resilience [?] researchers believe it could be crucial
  • for identifying which reef ecosystems
    • will withstand future climate changes.

Where [?] represents:

• Choice A: no punctuation
• Choice B: , and
• Choice C: ,
• Choice D: and,

Understanding the Meaning

The first sentence gives us the context:

• Recent studies of coral reefs have revealed something interesting -
  • certain coral species can adapt to warming ocean temperatures
  • more rapidly than scientists initially predicted.

So we're learning that some corals are better at handling warmer water than expected.

Now the second sentence tells us more about this:

• "This phenomenon is termed thermal resilience"
  • This gives a name to what was just described
  • "Thermal resilience" is what we call the ability to adapt to temperature changes

This is where we have the blank.

Let's look at the choices:

• They're asking us to decide what punctuation (if any) comes after "resilience"
• Our options are: nothing, comma + and, just comma, or and + comma

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

• "researchers believe it could be crucial for identifying which reef ecosystems will withstand future climate changes"
  • So researchers think this thermal resilience concept
  • could help them figure out which reefs will survive climate change

What do we notice about the structure here?

• "This phenomenon is termed thermal resilience"
  • This is a complete thought - it could stand alone as its own sentence
  • It has a subject (This phenomenon), a verb (is termed), and completes the idea

• "researchers believe it could be crucial for identifying which reef ecosystems will withstand future climate changes"
  • This is ALSO a complete thought - it could also stand alone
  • It has a subject (researchers), a verb (believe), and completes its own idea

So we have two complete thoughts that are being connected in one sentence.

When we connect two complete thoughts like this, we can't just run them together with nothing, and we can't use just a comma by itself. We need a comma + a connecting word like "and."

The correct answer is Choice B: resilience, and

This properly connects the two complete thoughts with a comma followed by "and."

GRAMMAR CONCEPT APPLIED

Connecting Two Complete Thoughts

When you have two complete thoughts (called independent clauses in grammar terms) that you want to put in the same sentence, you need to connect them properly. You can't just run them together or use only a comma.

The standard ways to connect two complete thoughts:

1. Comma + coordinating conjunction:
   • First complete thought, and second complete thought
   • First complete thought, but second complete thought
   • Other coordinating conjunctions: or, nor, for, so, yet
2. Why just a comma doesn't work:
   • First complete thought, second complete thought (comma splice)
   • First complete thought, and second complete thought (correct)
3. Why no punctuation doesn't work:
   • First complete thought second complete thought (run-on sentence)
   • First complete thought, and second complete thought (correct)

In our question:

• "This phenomenon is termed thermal resilience" = complete thought
• "researchers believe it could be crucial for identifying which reef ecosystems will withstand future climate changes" = complete thought
• We need: resilience, and researchers to properly connect them

The comma + "and" structure properly joins these two related ideas into one well-constructed sentence.