Marine biologists studying the effects of ocean warming have discovered that while some coral species demonstrate unexpected resilience to temperature...

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

• Marine biologists
  • studying the effects of ocean warming
• have discovered that
  • while some coral species demonstrate unexpected resilience
    • to temperature changes [?]
  • the majority of reef-building corals show significant bleaching
    • when water temperatures rise beyond historical norms.

Where [?] is:

• A: colon (:)
• B: semicolon (;)
• C: comma (,)
• D: nothing

Understanding the Meaning

Let's start reading from the beginning:

'Marine biologists studying the effects of ocean warming have discovered that...'

So we're learning about a discovery that marine biologists made. What did they discover?

'...while some coral species demonstrate unexpected resilience to temperature changes...'

This is where we have the blank. Let's look at the choices:

• We're deciding what punctuation (if any) should come after 'changes'
• The options are: colon, semicolon, comma, or nothing

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

'...the majority of reef-building corals show significant bleaching when water temperatures rise beyond historical norms.'

Now let's understand the complete picture of what the biologists discovered:

• 'While some coral species demonstrate unexpected resilience to temperature changes'
  • This tells us one fact: some corals handle the warming surprisingly well
• 'The majority of reef-building corals show significant bleaching when water temperatures rise beyond historical norms'
  • This tells us a contrasting fact: most reef-building corals don't handle it well - they bleach

So the discovery has two parts that contrast with each other:

• Some corals are resilient (the surprising part)
• BUT most reef-building corals suffer bleaching (the concerning part)

What do we notice about the structure here?

• The word 'while' at the start of the first part is key
  • 'While' introduces a subordinate thought - it's setting up background information or a contrast
  • This 'while' part can't stand alone as a complete sentence
• The second part 'the majority of reef-building corals show significant bleaching...'
  • This IS a complete thought with its own subject and verb
  • This is the main statement
• When you have a subordinate part (starting with 'while') that comes BEFORE the main statement, you need a comma to separate them
  • The comma shows the reader: "Here's where the introductory/background information ends and the main point begins"

The correct answer is C: changes, (with comma).

GRAMMAR CONCEPT APPLIED

Using Commas After Introductory Subordinate Clauses

When a subordinate clause (also called a dependent clause in grammar terms) comes at the beginning of a sentence, you need a comma to separate it from the main clause. Subordinate clauses often start with words like "while," "although," "because," "when," "if," "since," or "as."

The Pattern:

• Subordinate clause (starts with subordinating word), main clause.
• Example: "While I enjoy summer, I prefer autumn."
• "While I enjoy summer" = subordinate clause (can't stand alone)
• "I prefer autumn" = main clause (complete thought)
• Comma separates them

Why the comma is needed:

• The comma acts as a signal to readers: "The introductory/background information is ending, and now the main point is starting"
• Without it, the sentence feels rushed and confusing

In our question:

• Subordinate clause: "while some coral species demonstrate unexpected resilience to temperature changes"
  • Starts with "while"
  • Provides contrasting background information
  • Cannot stand alone
• Main clause: "the majority of reef-building corals show significant bleaching when water temperatures rise beyond historical norms"
  • Complete thought
  • The primary statement being made
• Result: changes, the majority (comma needed)

Quick check: If you can move the subordinate clause to the end of the sentence without the comma, it confirms it's a subordinate clause:

• "The majority of reef-building corals show significant bleaching while some coral species demonstrate unexpected resilience" (no comma needed when subordinate clause comes second)