SAT OwlQuestion bank / Text Structure and Purpose
Ancient Roman concrete has survived for two thousand years in harbor walls battered by seawater, while many modern concrete structures crumble within decades. A team of geologists set out to learn why. They found that when seawater seeped into the Roman concrete, it reacted with volcanic ash in the mix to grow new minerals, including a rare crystal called aluminous tobermorite, that filled cracks and strengthened the material over time. Modern concrete, by contrast, is designed to be chemically stable, so it gains no such benefit.
Which choice best describes the overall structure of the text?
It presents a contrast between two materials, describes research into the cause of that contrast, and reports what the researchers found.
It describes a problem with modern concrete and then proposes a specific method for fixing it.
It explains how Roman engineers designed their concrete and argues that modern engineers should copy them.
It describes a scientific debate and then explains why the debate remains unresolved.
Show answer and explanation
Answer: A
The text opens by contrasting durable Roman concrete with modern concrete, says geologists investigated why, and then reports the explanation: seawater reactions that grew strengthening minerals. Choice A follows that order.
Choice C adds an argument the text never makes; it explains a difference but does not tell modern engineers what to do.
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