Obsidian is a kind of volcanic glass formed when lava cools so quickly that the atoms inside it cannot arrange...
GMAT Standard English Conventions : (Grammar) Questions
Obsidian is a kind of volcanic glass formed when lava cools so quickly that the atoms inside it cannot arrange themselves in a crystalline structure. You _______ more about obsidian's structure, which is classified as amorphous, in a later chapter.
Which choice completes the text so that it conforms to the conventions of Standard English?
had learned
had been learning
will learn
have learned
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
Sentence 1:
- Obsidian is a kind of volcanic glass
- formed when lava cools so quickly
- that the atoms inside it cannot arrange themselves
- in a crystalline structure.
- that the atoms inside it cannot arrange themselves
- formed when lava cools so quickly
Sentence 2:
- You [?] more about obsidian's structure,
- which is classified as amorphous,
- in a later chapter.
Understanding the Meaning
The first sentence gives us some scientific background:
- Obsidian is a type of volcanic glass
- It forms when lava cools so fast that atoms can't organize into crystals
This is just setting up the context for us.
Now the second sentence addresses the reader directly:
- "You ______ more about obsidian's structure, which is classified as amorphous..."
This is where we have the blank. Let's look at the choices:
- They're all different forms of "learn" - but in different time frames
- A. had learned (past)
- B. had been learning (past)
- C. will learn (future)
- D. have learned (past/present)
To see what works here, let's read the rest of the sentence and understand what it's saying!
The sentence ends with: "in a later chapter."
This is the key phrase! Let's think about what this means:
- "In a later chapter" means in a future chapter - one that comes after this one
- This tells us WHEN the learning will happen
- It's something that hasn't occurred yet but will happen in the future
What do we notice about the structure here?
The phrase "in a later chapter" is a time marker that points to the future. When a sentence tells us something will happen at a future time, we need a verb tense that matches that future time frame.
So we need will learn - the simple future tense that matches the future time indicated by "in a later chapter."
The correct answer is C.
GRAMMAR CONCEPT APPLIED
Matching Verb Tense to Time Markers
When a sentence includes words or phrases that tell you WHEN something happens (called time markers), your verb tense must match that time frame. Think of it as keeping your timeline consistent.
Future time markers → Future tense verbs
- "Tomorrow we will discuss the results"
- "Tomorrow" signals future → needs "will discuss" (not "discussed" or "have discussed")
- "Next year, scientists will launch the satellite"
- "Next year" signals future → needs "will launch"
In this question:
- Time marker: "in a later chapter"
- This clearly indicates future time (a chapter that comes later)
- Correct verb: "will learn"
- Simple future tense that matches the future time frame
The pattern:
- Identify the time marker in the sentence
- Determine what time frame it indicates (past, present, or future)
- Choose the verb tense that matches that time frame
had learned
✗ Incorrect
- This is past perfect tense, which describes something that happened before another past event
- But "in a later chapter" clearly refers to the future, not the past
- Using past tense for a future event creates an impossible timeline
had been learning
✗ Incorrect
- This is past perfect continuous tense, showing an ongoing action in the past
- Like Choice A, this is past tense, but the sentence needs future tense
- The time marker "in a later chapter" indicates future time, not past
will learn
✓ Correct
Correct as explained in the solution above.
have learned
✗ Incorrect
- This is present perfect tense, which describes something that happened at an unspecified past time
- But the sentence explicitly states the learning will happen "in a later chapter" - in the future
- This tense mismatch makes the sentence illogical