16Hit1600
Expression of IdeasEasy–MediumRhetorical synthesis (concluding a text to meet a stated goal)

Expression of Ideas practice question

Cactus spines do more than fend off hungry animals. Studying barrel cacti in Mexico's Chihuahuan Desert, botanist Elena Vargas noticed that the spines' finely grooved surfaces catch droplets of nighttime fog and funnel them down toward the plant's base, where shallow roots take up the moisture. In her measurements, a single cactus channeled several milliliters of water to its roots overnight. ______

The student wants to conclude the text by identifying a practical application of Vargas's findings. Which choice most effectively accomplishes this goal?

  1. A. Engineers have begun designing fog-collecting mesh panels modeled on the grooves of these spines, aiming to supply drinking water in arid communities.Correct
  2. B. Barrel cacti can survive for more than a century in some desert environments.
  3. C. Cactus spines, then, are far more sophisticated structures than most people assume.
  4. D. Other researchers question whether fog contributes much to a barrel cactus's total water intake.

Answer: A. Engineers have begun designing fog-collecting mesh panels modeled on the grooves of these spines, aiming to supply drinking water in arid communities.

A is correct: it describes a real-world use—fog-collecting panels for drinking water—derived from the grooved-spine mechanism the text explains. B adds an unrelated fact about cactus lifespan and offers no application. C restates the general significance of the findings, which a student may confuse with an application, but no use of the discovery is named. D introduces a counterargument rather than an application, reversing the requested rhetorical purpose.

Why the other answers are wrong

B. Barrel cacti can survive for more than a century in some desert environments.
Cactus lifespan is a new, unrelated fact — it says nothing about a use for Vargas's discovery.
C. Cactus spines, then, are far more sophisticated structures than most people assume.
This restates why the findings matter, which is close but not the same as naming a practical application; no real-world use of the grooved spines is mentioned.
D. Other researchers question whether fog contributes much to a barrel cactus's total water intake.
This raises a challenge to Vargas's findings rather than a use for them, which is the reverse of the requested purpose.

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