Question:
Goal: how to be quiet?

Which of the following methods is more reasonable for accomplishing this goal?
Answer:
make very little noise

Question:
Goal: To save on buying water,

Which of the following methods is more reasonable for accomplishing this goal?
Answer:
use a rain catcher such as a barrel and route the roof gutters to it, then purify the collected water.

Question:
Goal: paper towel

Which of the following methods is more reasonable for accomplishing this goal?
Answer:
protect telescope