What Is the Origin of Smooth Troughs (T on This

question 25

Multiple Choice

What is the origin of smooth troughs (T on this figure) cutting across the landscape in the Great Lakes area?

• A)The areas were covered by soft marine sediments.
• B)A huge flood coming from Iowa flowed toward the Great Lakes.
• C)Glaciers carved the smooth troughs.
• D)All of these.

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