A 2023 study by climate scientist Dr. Helena Vasquez identified three interconnected environmental threats facing coastal ecosystems: accelerating gla...

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

• A 2023 study
• by climate scientist Dr. Helena Vasquez
• identified three interconnected environmental threats
• facing coastal ecosystems:
• accelerating glacial melt(?)
• rising sea surface temperatures, and
• increased frequency of severe storms.

Understanding the Meaning

• Let's start reading from the beginning:
  • tells us who conducted the research
• identified three interconnected environmental threats facing coastal ecosystems:
  • This is the key part - the study identified THREE threats
  • The colon here signals: 'here comes the list of those three threats'
• This is where we have the blank: 'accelerating glacial melt(?).'
• Let's look at the choices:
  • The choices give us different punctuation marks: colon, comma, nothing, or semicolon
  • To see what works here, let's read the rest of the sentence and understand what it's saying!
• The sentence continues:
  • 'accelerating glacial melt(?) rising sea surface temperatures, and increased frequency of severe storms'
• Now I can see the complete picture:
  • The sentence promises THREE threats
  • Then it lists them:
    1. accelerating glacial melt
    2. rising sea surface temperatures
    3. increased frequency of severe storms
• What do we notice about the structure here?
  • This is a standard list of three items
  • Items 2 and 3 are connected with ', and'
  • This follows the typical list pattern: Item 1, Item 2, and Item 3
  • Each item is a noun phrase describing a threat
• So we need a comma after 'melt' to separate the first item in the list from the second item - just like we use commas to separate items in any three-item list.

The correct answer is B (melt,).

GRAMMAR CONCEPT APPLIED

Using Commas to Separate Items in a List

When you list three or more items in a sentence, you use commas to separate them (called items in a series in grammar terms). The standard pattern is:

Pattern: Item 1, Item 2, and Item 3

Example 1 - Simple list:

• The store sells apples, oranges, and bananas.
  • Three items: apples / oranges / bananas
  • Commas separate each item

Example 2 - List of phrases:

• The candidate promised lower taxes, better schools, and improved healthcare.
  • Three items (noun phrases): lower taxes / better schools / improved healthcare
  • Commas separate each item

How this applies to our question:

• The sentence announces 'three interconnected environmental threats'
• These three threats are listed:
  1. accelerating glacial melt
  2. rising sea surface temperatures
  3. increased frequency of severe storms
• Commas must separate these items, so we need a comma after 'melt'