Archaeological site dating relies heavily on radiocarbon analysis, which can accurately determine the age of organic materials found at excavation...
GMAT Expression of Ideas : (Expression) Questions
Archaeological site dating relies heavily on radiocarbon analysis, which can accurately determine the age of organic materials found at excavation sites. This method works well for artifacts up to about 50,000 years old and provides precise chronological information. Potassium-argon dating can reach back millions of years and offers much greater temporal range; _____ it requires volcanic material and cannot be applied to most archaeological contexts.
Which choice completes the text with the most logical transition?
however,
for instance,
therefore,
likewise,
Step 1: Decode and Map the Passage
Create Passage Analysis Table
| Text from Passage | Analysis |
|---|---|
| "Archaeological site dating relies heavily on radiocarbon analysis, which can accurately determine the age of organic materials found at excavation sites." |
|
| "This method works well for artifacts up to about 50,000 years old and provides precise chronological information." |
|
| "Potassium-argon dating can reach back millions of years and offers much greater temporal range;" |
|
| "it requires volcanic material and cannot be applied to most archaeological contexts." |
|
Provide Passage Architecture & Core Elements
Main Point: Archaeological dating uses different methods with distinct advantages and limitations - radiocarbon for recent precision, potassium-argon for extended range but limited applicability.
Argument Flow: The passage establishes radiocarbon as the primary dating method with specific strengths and time limits. It then introduces potassium-argon dating as having superior temporal range, but sets up a contrast by revealing its practical limitations for most archaeological work.
Step 2: Interpret the Question Precisely
This is a fill-in-the-blank question asking us to choose the best logical connector. The answer must create the right relationship between what comes before and after the blank.
Step 3: Prethink the Answer
- Looking at our analysis, potassium-argon dating is presented with a major advantage (millions of years, much greater temporal range), but the sentence after the blank reveals a significant drawback (requires volcanic material, cannot be used in most archaeological contexts)
- The logical relationship here is contrast - we are moving from highlighting an advantage to revealing a limitation
- The transition should signal that despite the previous positive information, there is a problem or restriction coming
however,
- Correct - Creates the perfect contrast between K-Ar advantages and its practical limitations
- "However" signals that despite the greater temporal range mentioned, there is a significant restriction coming
- Matches our prethinking about needing a contrast transition
for instance,
- Incorrect - "For instance" suggests the following information will be an example or illustration
- But the limitation is not an example of the temporal range - it is a contrasting drawback
- This would make the sentence illogical
therefore,
- Incorrect - "Therefore" indicates the following information is a logical result or conclusion
- The volcanic material requirement is not caused by having greater temporal range
- Creates a false cause-and-effect relationship
likewise,
- Incorrect - "Likewise" suggests similarity or agreement with what came before
- But the limitation contradicts rather than supports the advantage
- Students might think both sentences are about K-Ar dating so they should connect similarly, missing that one shows advantages while the other shows disadvantages