About 70,000 meteorites have been found on Earth. Although most meteorites are fragments of _______ hundred have been identified as...

Sentence Structure

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!

• About 70,000 meteorites have been found on Earth.
• Although most meteorites are fragments of asteroids[?]
  • several hundred have been identified
    • as being from the Moon or Mars.

Understanding the Meaning

Let's start from the beginning:

'About 70,000 meteorites have been found on Earth.'

• This opening sentence tells us the general fact - we've found a lot of meteorites (space rocks that have landed on Earth).

Now the second sentence begins:
'Although most meteorites are fragments of asteroids...'

• This starts with 'Although' - which signals we're setting up a contrast
• It's telling us what's true for MOST meteorites (they come from asteroids)
• But 'although' tells us there's a 'but' coming - something different is about to be mentioned

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

• A: period (making two separate sentences)
• B: comma
• C: semicolon
• D: colon

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

'several hundred have been identified as being from the Moon or Mars'

• This is the contrasting information
• While MOST meteorites are from asteroids, SOME (several hundred) are actually from the Moon or Mars
• This part has its own subject ('several hundred') and verb ('have been identified')

What do we notice about the structure here?

• The first part - 'Although most meteorites are fragments of asteroids' - is a dependent clause
  • It starts with 'although' which makes it incomplete on its own
  • It can't stand alone as a sentence - it needs to connect to a complete thought
• The second part - 'several hundred have been identified as being from the Moon or Mars' - is an independent clause
  • This is the main, complete thought of the sentence
  • It could stand alone as a sentence
• When a dependent clause starting with a word like 'although' comes BEFORE an independent clause, we use a comma to separate them

So we need Choice B: comma - to properly connect the dependent clause to the independent clause that completes the sentence.

GRAMMAR CONCEPT APPLIED

Using Commas After Introductory Dependent Clauses

When you start a sentence with a word like "although," "because," "while," "if," or "when," you create a dependent clause (called a subordinate clause in grammar terms) that cannot stand alone. This introductory dependent clause must be followed by a comma before the independent clause that completes the sentence:

Pattern: Dependent Clause + COMMA + Independent Clause

Example 1:

• Although the weather was terrible, we decided to go hiking.
  • Dependent clause: "Although the weather was terrible"
  • Independent clause: "we decided to go hiking"
  • Comma separates them

Example 2:

• Because students studied hard, the class average improved significantly.
  • Dependent clause: "Because students studied hard"
  • Independent clause: "the class average improved significantly"
  • Comma separates them

In our question:

• Although most meteorites are fragments of asteroids, several hundred have been identified as being from the Moon or Mars.
  • Dependent clause: "Although most meteorites are fragments of asteroids"
  • Independent clause: "several hundred have been identified as being from the Moon or Mars"
  • Comma properly separates them

The comma signals to the reader: "The introductory context is complete; now here comes the main point."