The active voice sentence is "We have kept the bird in the cage too long." Choose the option that best expresses this sentence in the passive voice.

Introduction / Context:
This question checks conversion from present perfect tense in active voice to present perfect passive voice. The original sentence expresses regret or criticism that "we" have kept the bird in a cage for a longer time than is appropriate. In the passive version, the focus moves to "the bird" while the sense of extended duration and present relevance remains intact.

Given Data / Assumptions:

• Active sentence: We have kept the bird in the cage too long.
• Subject: we.
• Object: the bird.
• Verb phrase: have kept (present perfect).
• Additional phrase: in the cage too long, indicating location and excessive duration.

Concept / Approach:
Present perfect passive voice uses the pattern: subject (former object) + has/have been + past participle. In this case, "the bird" becomes the subject, and "have kept" converts to "has been kept" because "bird" is singular. We maintain the phrase "in the cage" and add "for too long" to express the extended duration clearly. The agent phrase "by us" shows who performed the action, though it could be omitted in ordinary usage.

Step-by-Step Solution:

Step 1: Identify "the bird" as the object that will become the subject of the passive sentence. Step 2: Change "have kept" to the singular present perfect passive form "has been kept," because the subject "the bird" is singular. Step 3: Retain the phrase "in the cage" to show the place of confinement and add "for too long" to show excessive duration. Step 4: Add "by us" as the agent phrase. The final passive sentence is: "The bird has been kept in the cage by us for too long."

Verification / Alternative check:
The sentence "The bird has been kept in the cage by us for too long" matches the required structure and preserves the meaning of the original. It clearly indicates that the bird is still affected by this past action, which is characteristic of present perfect. The phrase "for too long" keeps the sense of excess duration.

Why Other Options Are Wrong:

Option B: "Keeping of the bird in the cage has been done by us for too long." is unnecessarily complex and unnatural due to the nominalisation "keeping of the bird." Option C: "We have been keeping for long the bird in the cage." is active and uses an unusual word order; it also weakens the clear sense of "too long." Option D: "The bird would have been kept in the cage by us for too long." uses "would have been kept," changing the meaning to a hypothetical or conditional situation rather than a real completed action. Option E: "The bird is kept in the cage too long by us." uses simple present instead of present perfect, so it does not reflect the same time frame as the original sentence.

Common Pitfalls:
Some learners forget to switch from "have" to "has" when the new subject is singular, leading to agreement errors. Others drop "been" and create incomplete passive forms like "has kept." There is also a tendency to remove or change the degree of duration (for example, using "for long" instead of "for too long"), which alters the nuance. Always match both tense and idea while forming passive structures.

Final Answer:
The correct passive voice sentence is The bird has been kept in the cage by us for too long.