سُئِلَ: مَنْ حَضَرَ؟ فَقِيلَ: خَالِدٌ.
Someone asked, “Who attended?” The reply was, “Khalid.”
The nominative “Khālidun” may be explained through an elliptical nominal structure, depending on the grammatical analysis adopted. The question nonetheless supplies enough context to recover the intended message: Khalid attended.
Ellipsis is effective when the remaining expression makes the intended meaning recoverable. Where several incompatible restorations are possible, one should not invent a missing clause and assert it as the speaker’s certain intention.