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Craft and StructureMediumPurpose: explaining a mechanism

Craft and Structure practice question

A canal lock lets boats move between stretches of water at different heights. The boat enters a chamber, and gates close behind it. Sluices then let water in from the higher side, or out to the lower side, until the chamber's level matches the water ahead. Finally the far gates open and the boat continues.

Which choice best states the main purpose of the text?

  1. A. To explain how a mechanism works by describing its steps in order.Correct
  2. B. To argue that canals are more efficient than roads.
  3. C. To describe the history of a particular canal.
  4. D. To compare two ways of raising boats.

Answer: A. To explain how a mechanism works by describing its steps in order.

Enter, close, fill or drain, open.

Why the other answers are wrong

B. To argue that canals are more efficient than roads.
No argument about roads.
C. To describe the history of a particular canal.
No history, no particular canal.
D. To compare two ways of raising boats.
One method only.

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