Step 1: Understanding the Concept:
Voice refers to the relationship between the action expressed by the verb and the participants identified by its arguments.
In Active Voice, the subject performs the action. In Passive Voice, the subject receives the action.
The conversion requires moving the object to the subject position and using the appropriate form of the auxiliary verb "to be" followed by the past participle (V3) of the main verb.
Step 2: Detailed Explanation:
Let's analyze the components of the active sentence: "They (Subject) completed (Verb - Simple Past) the project (Object) on time (Adverbial phrase)."
To transform this into the passive voice, follow these three logical steps:
1. Object-Subject Shift: The object "the project" becomes the new subject of our passive sentence.
2. Identify the Tense: The original verb "completed" is in the Simple Past Tense.
3. Apply the Passive Formula: For Simple Past, the formula is: Was/Were + Past Participle (V3).
Since "The project" is a singular noun, we must use "was." The V3 form of "complete" is "completed."
Resulting structure: "The project was completed on time."
Analysis of other options:
Option (B) "The project completed..." is incorrect because it implies the project performed the action itself.
Option (C) "The project is completed..." is incorrect because it changes the tense from past to present.
Option (D) "The project had completed..." is incorrect because it uses the Past Perfect tense, which was not the original aspect.
By following the rules of tense preservation, Option (A) is the only correct answer.
Step 3: Final Answer:
The correct passive voice sentence is option (A).