In the following question, a sentence is given in Active Voice. Choose the option that best expresses the same idea in Passive Voice: “Sarla changed the curtains.”

Introduction / Context:
This question tests knowledge of transforming a sentence from Active Voice to Passive Voice. In Active Voice, the subject performs the action. In Passive Voice, the focus shifts to the object, which becomes the grammatical subject of the sentence. Voice change questions are very common in competitive exams and help assess understanding of tense, agreement, and correct auxiliary verb usage.

Given Data / Assumptions:
Active sentence: “Sarla changed the curtains.”
We must express the same meaning in Passive Voice. The options include sentences with different tenses and structures. We assume standard rules: object of the active sentence becomes the subject of the passive sentence, and the main verb is rewritten as a form of “be” plus past participle.

Concept / Approach:
The original sentence is in the simple past tense: “changed”. The object is “the curtains”. In Passive Voice, “the curtains” must become the subject. The passive structure for simple past is “was or were + past participle”. Since “curtains” is plural, we use “were changed”. We then add the agent phrase “by Sarla” to show who performed the action. Therefore, the correct passive form is “The curtains were changed by Sarla.”

Step-by-Step Solution:
Step 1: Identify subject, verb, and object in the active sentence. Subject: Sarla, Verb: changed, Object: the curtains. Step 2: Move the object “the curtains” to the subject position in the passive sentence. Step 3: Convert the verb “changed” (simple past) into passive form “were changed”, because “curtains” is plural and simple past passive uses “was or were + past participle”. Step 4: Add the agent phrase “by Sarla” at the end to indicate who performed the action. Step 5: The resulting sentence is “The curtains were changed by Sarla.”

Verification / Alternative check:
Compare option (b) “The curtains were changed by Sarla” with the original sentence. Both clearly describe the same past action. If we convert it back to active voice, we again get “Sarla changed the curtains”, confirming that the meaning and tense are preserved. Checking other options: “Sarla changes the curtains” changes the tense to simple present. “The curtain was changed by Sarla” makes the object singular, which alters the meaning. “Sarla was the one by whom the curtains were changed” is grammatically possible but unnecessarily wordy compared to the standard passive transformation and is not the direct expected answer.

Why Other Options Are Wrong:
Option (a) uses present tense instead of past and fails to be passive; it remains active.
Option (c) changes “curtains” to singular “curtain”, which changes the meaning, and also does not match the exact object given.
Option (d) is an awkward and indirect construction. While it conveys roughly the same idea, exams typically expect the simplest and most direct passive form, which is option (b).

Common Pitfalls:
Students sometimes forget to maintain tense when shifting from active to passive and mistakenly move to present tense or another form. Another frequent mistake is failing to match subject verb agreement when using “was” and “were”. Always count the object and then choose the correct auxiliary verb. Also, avoid unnecessarily complicated structures when a simple passive form exists.

Final Answer:
The correct Passive Voice sentence is The curtains were changed by Sarla.