Please submit your concern

Explanation:

The main idea of the passage is how it is easier for something of a higher value to increase its value than the contrary.
Option A: Mnemonics means the study and development of systems for improving and assisting memory. Since this is not in the passage's scope, it is not the right answer.
Option B: This is totally the opposite of the viewpoints of the authors discussed in the passage and hence is not the right answer.
Option C: Since this option aptly captures the main idea of the passage, this is the correct answer.
Option D: Although the English language's example is used as an illustration, it is not the main idea of the passage.
Thus, the correct option is D.