In the following question, select the option that best expresses the meaning of the English idiom leave no stone unturned.

Introduction / Context:
This idiom question checks whether you understand the figurative meaning of leave no stone unturned. The phrase is widely used in newspapers, speeches, and everyday conversation to describe determined effort. You must select the option that matches this established figurative sense, not a literal picture of stones and treasure.

Given Data / Assumptions:

• Idiom: leave no stone unturned.• Options suggest different interpretations of effort and achievement.• We assume standard English usage in motivational and descriptive contexts.• The question focuses on describing effort, not literal physical actions.

Concept / Approach:
Leave no stone unturned comes from the idea of a person searching for something valuable by turning over every stone to check underneath. Figuratively, it means to use every possible method and make every possible attempt to achieve a goal or find something. It does not require that a hidden treasure actually exist, nor does it comment on the success level; it focuses on the completeness of effort. Therefore, the option that says try every possible course of action in order to achieve something is the correct match.

Step-by-Step Solution:
Step 1: Recall notices like The police left no stone unturned in their search for the missing child, which highlight thorough effort.Step 2: See that the emphasis is on trying every possible way, not only on a specific type of task.Step 3: Examine option D Try every possible course of action in order to achieve something, which accurately captures this idea.Step 4: Option A Search for the hidden treasure is too literal and limited to one context, not to general usage.Step 5: Option B Do a futile task incorrectly suggests that the effort is pointless, which is not part of the idiom's meaning.Step 6: Option C Be known for achieving a tremendous feat talks about fame and success, while the idiom is about effort, regardless of fame.

Verification / Alternative check:
Consider more examples. A candidate might say I left no stone unturned in preparing for the exam, meaning that he or she used all available resources and methods. The outcome may or may not be success, but the effort was complete. This exactly matches option D. No other option reflects the general and figurative nature of the idiom across different situations such as investigations, job searches, or problem solving.

Why Other Options Are Wrong:
Search for the hidden treasure takes the original literal story behind the idiom but does not describe the figurative sense used in modern English sentences. Do a futile task suggests that the effort is useless or cannot succeed, which is not implied by the idiom. Be known for achieving a tremendous feat shifts focus from effort to later recognition and achievement, which again is not intrinsic to the phrase. As a result, these options do not correctly explain the idiom.

Common Pitfalls:
Candidates sometimes choose very specific or dramatic sounding options instead of the one that captures the common, practical meaning. It is important to remember that idioms are used in many everyday contexts and usually have a broad, general meaning. Mentally replace the idiom in a simple sentence and test each option to see which keeps the overall sense intact.

Final Answer:
The idiom leave no stone unturned means Try every possible course of action in order to achieve something.