The correct answer is غائب ہونا (Ghaib hona), which means to disappear. The Urdu idiom "کافور ہونا" (Kafoor hona) literally translates to "to become camphor." Camphor is well-known for its property of sublimation, where it transitions directly from a solid to a gas, seemingly vanishing rapidly without leaving any residue. Therefore, when something is said to "کافور ہونا," it means it has completely vanished, disappeared quickly, or evaporated without a trace, much like camphor itself. This idiom is used to describe the sudden and complete disappearance of a person or an object.
Option B, نمودار ہونا (Namoodar hona - To appear), is incorrect because it is the exact opposite of the idiom's meaning. "کافور ہونا" signifies vanishing or ceasing to exist, while "نمودار ہونا" means to become visible or to emerge.
Option C, ساتھ چلنا (Saath chalna - To walk along/accompany), is incorrect. This option describes companionship or movement with someone, which bears no relation to the concept of disappearance conveyed by the idiom.
Option D, None, is incorrect because "غائب ہونا" (To disappear) accurately and precisely defines the meaning of the idiom, rendering this option invalid.