The correct option to change the sentence into an exclamatory sentence is: "Alas that youth should pass away!"

Here's why:

• "Alas" is an interjection used to express sorrow, regret, or grief. It effectively sets the tone of lament and emphasizes the speaker's sadness about the passage of youth.
• The other options don't fully capture the emotional weight and exclamation:
  • "Bravo!" expresses praise or applause, which is completely opposite to the intended meaning of sadness.
  • "It is sad that youth passes away!" maintains the declarative format and doesn't convey the strong emotion of an exclamation.
  • "Youth should not pass away." expresses a wish or desire, not the speaker's sadness about an inevitable reality.