Idiom: in each of the following questions, choose the alternative which best expresses the meaning of the idiom or phrase. Donkey's years

Introduction / Context:
This idiom question focuses on the informal British English expression donkey's years. It is commonly used in conversation to refer to a very long period of time. Knowing such idioms helps in understanding dialogues and passages in exams and in everyday usage.

Given Data / Assumptions:

• Idiom: donkey's years.
• Options: A decade, A long time, A century, Since school days, A few minutes.
• The expression is informal and implies a vague but very long duration, not a precise number of years.

Concept / Approach:
Donkey's years is used to mean a very long time, often with a sense of exaggeration. For example, I have not seen him for donkey's years means I have not seen him for a very long time. It does not refer specifically to ten years, one hundred years, or any fixed period such as school days. Therefore, the option A long time accurately captures the idiomatic sense without forcing a specific number.

Step-by-Step Solution:
Step 1: Recall where you might have heard this idiom, usually in sentences like We have known each other for donkey's years. Step 2: Understand that the speaker is simply saying for a very long time, not stating an exact count of years. Step 3: Compare each option and identify which one expresses an indefinite, extended period. Step 4: Choose A long time as the best explanation of the idiom.

Verification / Alternative check:
Test the options by substitution. I have not visited that place for donkey's years becomes I have not visited that place for a long time, which feels natural and keeps the meaning. Replacing it with for a decade or for a century would misrepresent the idiom, because the phrase is not tied to ten or one hundred years. Since school days is too specific and A few minutes is completely opposite in sense.

Why Other Options Are Wrong:

• A decade: Fixes the time period at ten years, which is not implied by the idiom.
• A century: Suggests one hundred years, an even more specific and extreme measure, not what the phrase normally intends.
• Since school days: Refers to a period starting from a particular life stage, not simply a long duration.
• A few minutes: Directly contradicts the idea of a very long time.

Common Pitfalls:
Some learners try to attach a precise duration to idioms because they see words like years or decades. However, donkey's years is intentionally vague, used to exaggerate long intervals in casual speech. The safest approach is to choose definitions that keep this vagueness, such as a long time, and avoid answers that give an exact numeric length unless the idiom clearly refers to one.

Final Answer:
Correct option: A long time.