Scientists studying climate patterns have made remarkable discoveries through ice core analysis. In their groundbreaking 1990s expedition to Antarctic...

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 studying climate patterns
• have made remarkable discoveries
• through ice core analysis.
• In their groundbreaking 1990s expedition to Antarctica,
• (when and where)
• nearly 40% of the research team
• [was/is/will be/is being] (?)
• from institutions in Norway and Sweden.

Understanding the Meaning

Let's start reading from the beginning:

The first sentence tells us:

• Scientists who study climate patterns have made remarkable discoveries through ice core analysis.
  • This sets up the general topic - climate research using ice cores.

Now the second sentence gives us specific information:

• 'In their groundbreaking 1990s expedition to Antarctica,'
  • This is important! It's telling us about a specific expedition.
  • Notice the time marker: '1990s expedition' - this happened in the past.

Now here's where we need to fill in the blank:

• 'nearly 40% of the research team ______ from institutions in Norway and Sweden.'

Let's look at our choices:

• They're asking us to choose between different tenses of the verb 'to be':
  • will be (future)
  • is (present)
  • was (past)
  • is being (present continuous)

What do we notice about the time context?

• The sentence says '1990s expedition'
  • The 1990s is clearly in the past - it already happened.
  • When we describe facts about something that happened in the past, we need to use past tense.

So we need was - the past tense form.

The complete sentence tells us:

• In their 1990s expedition to Antarctica, nearly 40% of the team was from institutions in Norway and Sweden.
  • This is describing a fact about that past expedition - where the team members came from.

GRAMMAR CONCEPT APPLIED

Matching Verb Tense to Time Context

When a sentence provides clear time markers, the verb tense must align with that time frame. This is a fundamental principle: the verb's tense should match when the action or state occurred.

Pattern:

• Past time marker → past tense verb
  • "In the 1990s expedition, 40% of the team was from Norway"
  • Time marker: "1990s expedition" (past)
  • Verb: "was" (past tense)

• Present time marker → present tense verb
  • "In today's research teams, 40% are from Norway"
  • Time marker: "today's" (present)
  • Verb: "are" (present tense)

• Future time marker → future tense verb
  • "In next year's expedition, 40% will be from Norway"
  • Time marker: "next year's" (future)
  • Verb: "will be" (future tense)

How this applies to our question:

The phrase "1990s expedition" is a clear past time marker. The 1990s already happened - it's historical. Therefore, when describing facts about that expedition (like where the team members came from), we must use past tense: "was."