Choose the best precursor-to-event mapping to complete the analogy: “Thunder : Rain :: ? : Night” Select the natural transition or sign that commonly precedes night.

Introduction / Context:
This analogy uses the “sign/precursor : event” pattern. Thunder commonly accompanies or precedes rainfall, signaling the weather change. We must choose a phenomenon that similarly signals the approach of night in daily cycles.

Given Data / Assumptions:

• Thunder may herald or accompany rainstorms.
• Dusk is the period of fading light after sunset leading into night.
• We seek a natural temporal transition, not an effect or state.

Concept / Approach:
Select the transitional sign that regularly leads to night. “Dusk” is the twilight interval that precedes and blends into night, matching the “signal/precursor” function that thunder plays for rain.

Step-by-Step Solution:
1) Establish relation type: precursor/sign → event.2) Identify the daily-cycle precursor to night: dusk.3) Confirm regularity and naturalness of the mapping.

Verification / Alternative check:
“Evening” is broader and not always an immediate precursor; “dark” is a state overlapping with night rather than a sign leading into it. “Dus” appears to be a misspelling and is not standard. “Cloud” does not causally relate to night.

Why Other Options Are Wrong:

• Dus: Misspelt/undefined.
• Dark: A condition during night, not a precursor.
• Evening: A larger time block; less precise than “dusk.”
• Cloud: Weather condition, unrelated to daily diurnal transition.

Common Pitfalls:
Picking a state (“dark”) rather than a sign; or a broad period (“evening”) rather than the immediate transition (“dusk”).

Final Answer:
Dusk