In the following idiom and phrase question, you must choose the option that best expresses the meaning of the expression "Leave no stone unturned". When someone is advised to "leave no stone unturned" in order to achieve something, what does this phrase mean?

Introduction / Context:
This question tests your understanding of a very common English idiom, Leave no stone unturned. This phrase frequently appears in motivational contexts, exam advice and news reports, especially when people are urged to make maximum effort. Knowing idiomatic meanings helps you understand reading comprehension passages and also improves your own expressive power in English.

Given Data / Assumptions:

• The idiom is Leave no stone unturned.
• The options include ideas of searching for treasure, doing futile work, achieving a tremendous feat, and trying every possible course of action.
• The phrase is often used when someone is preparing for exams, searching for a solution or working hard toward a goal.
• You must identify the explanation that matches the established figurative meaning.

Concept / Approach:
To leave no stone unturned originally conjures up the image of a person searching for something so carefully that they lift every stone to check underneath. Figuratively, it means to use every possible method and explore every option in order to achieve a desired result. The emphasis is on thoroughness and determination, not on whether the task is futile or leads to a spectacular achievement. Therefore, the focus in the correct option should be on trying every possible course of action, not on treasure, fame or waste of effort.

Step-by-Step Solution:
Step 1: Recall the common usage: The investigation team left no stone unturned in their search for the missing person. Here the phrase clearly means they tried all methods. Step 2: Read option D: Try every possible course of action in order to achieve something. This exactly matches the idea of thorough and determined effort. Step 3: Examine option A: Search for the hidden treasure. While the literal image of turning stones might suggest treasure hunting, the idiom in modern usage is not limited to treasure and is not about a specific object. Step 4: Examine option B: Do a futile task. The idiom is actually positive and encourages effort; it does not say the task is pointless. Step 5: Examine option C: Be known for achieving a tremendous feat. Awards or fame may or may not follow, but the idiom focuses on the effort made, not on fame or recognition. Therefore, option D is the only accurate explanation.

Verification / Alternative check:
Use the idiom in a sentence connected to exam preparation: If you want to clear this competitive exam, you must leave no stone unturned in your preparation. Here, the phrase clearly encourages the student to try every strategy, solve many practice papers, revise thoroughly and manage time well. It does not assure a tremendous feat; instead, it emphasises complete effort. It also does not suggest that the work is futile. These considerations confirm that trying every possible course of action is the true sense of the idiom.

Why Other Options Are Wrong:
Searching for hidden treasure is a literal interpretation that ignores the idiom very wide application. Doing a futile task suggests a waste of time, while leave no stone unturned usually implies necessary and worthwhile effort. Being known for a tremendous feat focuses on the result and fame; the idiom is actually about the process and effort. None of these options capture the core idea of exhaustive attempts from every angle, which is central to the expression.

Common Pitfalls:
Students sometimes get distracted by picturesque literal images and choose answers that seem imaginative rather than accurate. Another pitfall is confusing positive idioms of hard work with those that imply futility or madness. The key is to rely on how you actually see the expression used in news, books or teacher advice. Whenever you are unsure, try to create a simple sentence of your own with the idiom and then paraphrase it. This method usually guides you toward the correct meaning in exam options.

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