Choose the one-word substitute that best matches the given definition: shine with a bright but brief or irregular light.

Introduction / Context:
This vocabulary question tests your ability to identify an exact one-word substitute for a descriptive phrase. These questions are common in competitive exams because they measure both your word power and your precision in matching meanings. The phrase here describes a particular way in which light behaves, and you must choose the verb that captures this behaviour in standard English usage.

Given Data / Assumptions:
- The descriptive phrase is: shine with a bright but brief or irregular light.- The options are: Whimper, Flicker, Cower, Mutter.- Only one option should correctly describe a type of light or shining.- The other options relate to sounds or body posture, not light.

Concept / Approach:
To answer one-word substitution questions, you should first understand the exact meaning of the phrase and then check which option has that meaning. The phrase "shine with a bright but brief or irregular light" suggests a light that is not steady but goes on and off or becomes brighter and dimmer repeatedly. In English, the verb "flicker" precisely describes such behaviour of light. The other words describe crying softly, shrinking back in fear, or speaking in a low, unclear voice, none of which relate to light.

Step-by-Step Solution:
Step 1: Identify the key idea in the phrase: the light is bright but not steady; it is brief or irregular.Step 2: Recall that "flicker" is used for candles, flames, and screens when they glow unsteadily or appear and disappear quickly.Step 3: Consider the meaning of "whimper": to cry or make weak, complaining sounds, usually associated with people or animals.Step 4: Recall that "cower" means to bend or crouch down in fear or shame, usually referring to a person or animal's posture.Step 5: Remember that "mutter" means to speak in a low, indistinct voice, often expressing dissatisfaction or complaint.Step 6: Only "flicker" refers to the behaviour of light; therefore it is the correct one-word substitute.

Verification / Alternative check:
You can verify your choice by using each option in a test sentence that describes light: "The candle began to whimper", "The candle began to flicker", "The candle began to cower", "The candle began to mutter". Only "flicker" fits naturally in English; the others do not make sense because they describe emotional or vocal actions, not luminous behaviour. Additionally, dictionaries define "flicker" as to burn or shine with a wavering light, which matches the phrase in the question very closely.

Why Other Options Are Wrong:
Option "Whimper": Refers to a soft, weak cry or sound, and does not relate to light or shining.Option "Cower": Describes bending low in fear or shame; it is about body posture, not light.Option "Mutter": Refers to speaking softly and unclearly; again, it concerns sound, not illumination.

Common Pitfalls:
Students sometimes focus on the general negative tone of unfamiliar words and guess randomly instead of analysing the core meaning. Another common mistake is to misread the phrase and think it describes a sound rather than light. To avoid such errors, always identify the domain of the description first: light, sound, movement, emotion, or posture. Once you know that the phrase is about light, it becomes easier to eliminate options that clearly belong to other domains.

Final Answer:
The correct one-word substitute is Flicker, which means to shine with a brief or irregular, unsteady light.