In the following question, out of the four alternatives, select the alternative which best expresses the meaning of the idiom or phrase: Herculean task.

Introduction / Context:
This idiom question asks you to interpret the phrase Herculean task. Idioms and allusions based on Greek and Roman mythology are quite common in English, especially in higher level reading and in editorial writing. Recognising this particular reference will help you understand descriptions of challenges or responsibilities in many contexts.

Given Data / Assumptions:

• Idiom: Herculean task.
• Options: Important task, Motivating, Optional to do, Very difficult task.
• We must choose the meaning that most accurately reflects the idiom as it is normally used.
• The idiom is based on the mythological hero Hercules (Heracles), known for his extraordinary strength and his famous twelve labours.

Concept / Approach:
A Herculean task is a task that requires great strength, effort, or courage to complete. It is not just important; it is extremely hard or demanding, similar to the legendary labours of Hercules. Therefore, the correct interpretation emphasises the very difficult nature of the task, not simply its importance, motivational quality, or optional status.

Step-by-Step Solution:
Recall the mythological background: Hercules had to perform twelve nearly impossible labours, such as slaying dangerous creatures and completing gigantic physical challenges.Connect that background to modern usage: when a writer says rebuilding the city after the disaster was a Herculean task, they mean it was extremely difficult.Option “Important task” only indicates significance, not difficulty. Many tasks are important but not Herculean.Option “Motivating” describes something that inspires someone, which is not the central idea here.Option “Optional to do” conflicts with the usual sense of huge responsibility.Option “Very difficult task” captures the key idea that the job requires enormous effort and strength.

Verification / Alternative check:
Use the idiom in sample sentences: “Clearing all the backlogged files in one week is a Herculean task.” Replacing the idiom with “very difficult task” keeps the sentence's meaning intact: “Clearing all the backlogged files in one week is a very difficult task.” Replacing it with important task or motivating changes the meaning and weakens the emphasis on difficulty.

Why Other Options Are Wrong:
Important task fails because importance relates to value or impact, not effort required. Motivating is about emotional encouragement, not sheer challenge. Optional to do suggests you may choose to skip the task, which does not match the heroic, unavoidable nature implied by Herculean. None of these alternatives reflect the original mythological idea of great, almost superhuman difficulty.

Common Pitfalls:
Sometimes students confuse Herculean with either heroic or significant and choose important task. While a Herculean task can indeed be important, its defining feature is that it is extremely hard to accomplish. When dealing with idioms based on mythological names, try to recall the main trait of the mythic figure: Hercules is famous primarily for strength and difficult labours, not just for importance or motivation.

Final Answer:
The idiom “Herculean task” means a very difficult task that requires enormous effort or strength.