The paper on the desk is one (that I found in my book)?

The sentence "The paper on the desk is one (that I found in my book)?" is grammatically incorrect.

Here's how to fix it:

* Option 1: Remove the parentheses and add a comma: "The paper on the desk is one that I found in my book."

* Option 2: Keep the parentheses and remove the "one": "The paper on the desk is (that I found in my book)."

* Option 3: Combine the two options: "The paper on the desk is (one that I found in my book)."

The best option depends on the intended meaning and the context of the sentence.