In the following question, a sentence has been given in the Active/Passive voice. Out of the four alternatives suggested, select the option which best expresses the same sentence in the Passive voice: The puppy spilled the milk as it drank.

Introduction / Context:
Here you are tested on your ability to convert a simple past tense active sentence into a correct and natural Passive voice sentence. The original sentence is: "The puppy spilled the milk as it drank." The focus is on what happened to "the milk," so the Passive voice must make "the milk" the grammatical subject while keeping the time and meaning unchanged.

Given Data / Assumptions:

• Active sentence: The puppy spilled the milk as it drank.
• Subject: "The puppy."
• Object: "the milk."
• Tense: simple past ("spilled").
• Clause of time: "as it drank" (while the puppy was drinking).

Concept / Approach:
For simple past Active to Passive conversion, the structure is: object + "was/were" + past participle + "by" + subject. The object "the milk" becomes the subject in the Passive form, followed by "was spilt" (simple past passive). The agent "the puppy" is introduced with "by," and the time clause "as it drank" remains unchanged. The Passive sentence should be concise and grammatically smooth without unnecessary nominalisations.

Step-by-Step Solution:
Step 1: Identify the object: "the milk." Step 2: Move "the milk" to the subject position: "The milk ..." Step 3: Convert "spilled" to simple past Passive form: "was spilt." Step 4: Add the agent with "by": "... was spilt by the puppy ..." Step 5: Keep the time clause intact: "as it drank." Step 6: Final sentence: "The milk was spilt by the puppy as it drank."

Verification / Alternative check:
If we convert "The milk was spilt by the puppy as it drank" back into Active voice, we get "The puppy spilled the milk as it drank," which matches the original sentence in both meaning and tense. The event, the agent, and the timing of the action are all preserved, which confirms that option B is correct.

Why Other Options Are Wrong:
Option A: "Spilling of the milk has been done..." is unnecessarily wordy and uses present perfect tense "has been done," which changes the time reference from simple past to present perfect. Option C: "While drinking it the puppy has spilt the milk" again shifts to present perfect "has spilt" instead of simple past and has awkward word order. Option D: "The milk was being drunk..." introduces the progressive passive and then adds "when it was spilled," which makes the sentence clumsy and implies two separate actions rather than the simple single action in the original.

Common Pitfalls:
Many learners overcomplicate Passive structures by adding forms like "has been done," "was being," or by turning verbs into nouns ("spilling of"). In exam-style transformations, keep the same tense and avoid changing the aspect unless the meaning clearly demands it. Focus on moving the object to the subject position and choosing the correct "be" form plus past participle.

Final Answer:
The correct passive form is: "The milk was spilt by the puppy as it drank."