Identify the problem with sentence fragment below your oldest cousin?

The problem with the sentence fragment "below your oldest cousin?" is that it lacks a subject.

To be a complete sentence, it needs to have a subject (who or what is doing the action) and a verb (the action itself).

Here are some ways to turn the fragment into a complete sentence:

* Adding a subject: "The treasure was buried below your oldest cousin."

* Adding a subject and verb: "Look for the treasure below your oldest cousin."

* Making it a question: "Is the treasure buried below your oldest cousin?"