In this English grammar question on voice, a sentence in the active voice is given about a policeman carrying a baton. Out of the four alternatives, select the option that best expresses the same idea in the passive voice: The policeman carries a baton whenever he goes on a round.

Introduction / Context:
This question asks you to convert a simple present active sentence describing a regular action into passive voice. The original sentence highlights the policeman as the subject who carries a baton on every round. The passive version must highlight the baton as the subject while keeping the habitual nature of the action clear. Voice change exercises like this are common checks of basic grammar skills in many entrance and recruitment exams.

Given Data / Assumptions:

• The main verb "carries" is in simple present tense.
• The subject is "The policeman".
• The object is "a baton".
• The adverbial clause "whenever he goes on a round" shows the condition or occasion.
• The passive form should keep the same tense and the same conditional idea.

Concept / Approach:
As with other simple present sentences, passive voice is formed using "is / are + past participle". Here the object "a baton" becomes the subject of the passive sentence, so we use "is carried". The original subject "the policeman" appears at the end with "by the policeman". The clause "whenever he goes on a round" remains unchanged, because it still correctly describes the circumstance under which the baton is carried. The result is a passive sentence that preserves the meaning and tense of the original active sentence.

Step-by-Step Solution:
First, identify "a baton" as the object that will become the new subject in the passive sentence. Second, note that the tense is simple present, so the correct auxiliary for the singular subject "baton" is "is". Third, create the passive verb phrase "is carried" using the past participle of "carry". Fourth, place "by the policeman" after the verb phrase to indicate who performs the action. Fifth, keep the clause "whenever he goes on a round" unchanged and place it after the main verb phrase.

Verification / Alternative check:
The passive sentence "A baton is carried by the policeman whenever he goes on a round" clearly preserves the original meaning. It still communicates that on every round, the policeman has a baton with him. The tense is simple present, and the condition "whenever he goes on a round" remains exactly the same. Reading both sentences together, you can see that the focus changes from the policeman to the baton, but the information does not change.

Why Other Options Are Wrong:
Option A uses an unnatural nominal pattern "Carrying of a baton is done" and also introduces the present perfect "has gone", which changes the sense and tense. Option B no longer attempts a passive transformation and instead introduces a negative idea about never going without a baton, which changes the meaning. Option C has an awkward and incorrect structure and does not present a clear passive form. Only option D follows the correct passive pattern "A baton is carried by the policeman" and retains the clause "whenever he goes on a round".

Common Pitfalls:
A typical mistake is to overcomplicate the sentence by using extra auxiliaries or nominal expressions like "carrying of". Another error is to shift to a different tense such as present perfect when there is no need. Some learners also wrongly change the clause "whenever he goes on a round", thus altering the condition under which the action happens. To avoid these issues, stick to the simple rule "be + past participle" for the same tense and move only the subject and object while leaving adverbial clauses intact whenever possible.

Final Answer:
The option that correctly expresses the sentence in the passive voice is: A baton is carried by the policeman whenever he goes on a round.