Verification of truth — necessary component: A window always has what?

Introduction / Context:
Unlike “cupboard,” the term “window” is broader and refers to an opening that admits light/air and often allows viewing. The question is which of the listed components a window must always have.

Given Data / Assumptions:

• Windows can be glazed or unglazed, grilled or not, curtained or bare, depending on culture, climate, and design.
• We are testing universality, not typicality.

Concept / Approach:
Check each candidate for universal necessity. “Curtain” is decorative/functional but optional. “Panes” (glass) are common but not required; many traditional windows lack glazing. “Grill” is a security element, not universal. Hence none of the given components is mandatory in all windows.

Step-by-Step Solution:

Verification / Alternative check:
Consider vernacular architecture (unglazed openings) or modern designs (frameless openings); the listed parts are not guaranteed.

Why Other Options Are Wrong:

• Curtain/Panes/Grill: Each is optional depending on context.
• All of these: Overstates necessity; false.

Common Pitfalls:

• Assuming glass panes are definitional; they are prevalent but not logically required.

Final Answer:

None of these