Correct Answer:
C. The work has been completed
The task is to find the correct passive voice for the sentence: "They have completed the work."
The original sentence is in the present perfect active voice, indicating an action that started in the past and has a connection to the present, or was completed at an unspecified time before now. To form the present perfect passive voice, the structure is: object + has/have + been + past participle of the main verb + (by agent).
- C: The work has been completed. This is the correct passive voice. 'The work' (the object) becomes the subject. Since 'the work' is singular, 'has' is used. The verb 'have completed' (present perfect active) correctly transforms into 'has been completed' (present perfect of 'to be' + 'been' + past participle). The agent 'by them' is omitted as it's often unnecessary when the focus is on the action or result.
- A: The work was completed. This is in the past simple passive voice ('was completed'), incorrectly changing the tense from present perfect to past simple.
- B: The work has completed. This remains in the active voice and implies 'the work' itself performed the action, which is grammatically incorrect.
- D: The work is completed. This is in the present simple passive voice ('is completed'), which changes the tense and aspect from present perfect.