SAT OwlQuestion bank / Text Structure and Purpose
Visitors to medieval churches sometimes notice that old windowpanes are thicker at the bottom than at the top, and a popular explanation holds that glass is a slow-moving liquid that has sagged over the centuries. Studies of glass, however, show that at room temperature it would take far longer than the age of the universe for any such flow to be visible. The uneven panes are better explained by how early glass was made: the methods of the time produced sheets of uneven thickness, and builders often set the heavier edge at the bottom.
Which choice best states the main purpose of the text?
To describe the methods medieval glassmakers used to color the glass in church windows
To argue that old church windows should be replaced with modern glass
To explain why glass is classified as a liquid
To correct a popular explanation for a feature of old windows and offer a better one
Show answer and explanation
Answer: D
The text presents the popular idea that glass flowed downward, shows that this flow would take far too long, and then gives a better explanation based on how early glass was made and installed. That is choice D.
Choice C repeats the popular claim that the text sets out to reject.
Why the other choices are wrong
- A. The text says nothing about coloring glass. It is about why old panes are uneven.
- B. The text makes no recommendation about replacing windows.
- C. The text rejects the idea that glass flows at room temperature.
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