Analogy — Part–of–whole (entry structure): House : Door :: Compound : ? Pick the feature that relates to “Compound” as “Door” relates to “House” (principal entry).

Introduction / Context:
The pair suggests a “principal entry of an enclosure.” A door is the designed entry into a house; correspondingly, the usual controlled entry into a compound is through its gate.

Given Data / Assumptions:

• House → Door (main access).
• Compound → ? (main access element among gate, fence, foundation, wall).

Concept / Approach:
Maintain the functional relationship “enclosure : primary access point.” The element must be the designed portal, not just any boundary component.

Step-by-Step Solution:

Verification / Alternative check:
Replace “House : Door” with “Compound : Gate” in everyday usage; the analogy reads naturally.

Why Other Options Are Wrong:

• Fence/Wall: Elements of enclosure; not an access point.
• Foundation: Structural base; unrelated to ingress.
• None of these: Invalid since “Gate” fits.

Common Pitfalls:
Selecting a boundary element because it “belongs” to a compound but missing the access function that “door” signals in the stem.

Final Answer:
Gate