Concept:
This is a passage-based question.
Such questions usually require selecting the option closest to the wording and meaning used by the author.
Step 1: Understand the question.
The question asks:
\[
\text{Enjoyment is the motto of whom?}
\]
So we must identify the group mentioned in the passage.
Step 2: Use the passage meaning.
According to the passage, enjoyment is described as the motto of the broad majority of present-day youth.
This means the author is not referring to a small rebellious group or a special group of youth.
The author refers generally to:
\[
\text{the vast majority of youth today}
\]
Step 3: Check the options.
Option (A) is too specific and not the best answer.
Option (B) refers only to rebellious youth, which is not the passage’s meaning.
Option (C) refers to youth looking for alternative development, which is not correct here.
Option (D) matches the passage idea.
Hence, the correct answer is:
\[
\boxed{(D)\ \text{vast majority of the youth today}}
\]