Understanding Sentence Improvement and Grammar Rules

Let's analyze the given sentence: "A better example is a person who (has been assigned) the duty of planting trees and watering them along an expressway." We need to determine if the bracketed part, "(has been assigned)", is grammatically correct in this context or if one of the alternatives improves it.

Analyzing the Subject and Verb Agreement

The key to checking the verb form here is identifying the subject it refers to. The phrase "who (has been assigned)" refers back to the noun "a person".

• The subject is "a person".
• "A person" is a singular noun.
• In English grammar, a singular subject requires a singular verb form in the present tense.

Analyzing the Verb Tense and Voice

The bracketed part "(has been assigned)" uses the present perfect tense ("has been") and the passive voice ("been assigned").

• Present Perfect Tense: Formed with "has" or "have" + past participle. It is used for actions that started in the past but are connected to the present.
• Passive Voice: Used when the subject receives the action. It is formed with a form of "be" + the past participle of the main verb. In the present perfect passive, the structure is "has/have been" + past participle.

In the sentence, "a person" is not performing the action of assigning; the action of assigning is being done to the person. Therefore, the passive voice is appropriate.

Evaluating the Bracketed Phrase "(has been assigned)"

Let's check if "(has been assigned)" correctly follows the rules for a singular subject ("a person") in the present perfect passive voice:

• The subject is "a person" (singular).
• The auxiliary verb for a singular subject in the present perfect is "has".
• The auxiliary for the passive voice is "been".
• The past participle of the verb "assign" is "assigned".

Combining these, the correct form for a singular subject in the present perfect passive is "has been assigned". This matches the bracketed phrase.

Examining the Improvement Options

Let's look at the given options:

1. have been assigned: The auxiliary verb "have" is plural. This would be correct if the subject were plural (e.g., "persons who have been assigned"), but the subject here is singular ("a person"). Incorrect.
2. have been assign: The auxiliary verb "have" is plural (incorrect for a singular subject). Also, "assign" is the base form, not the past participle needed for the passive voice and the present perfect tense. Incorrect.
3. has been assign: The auxiliary verb "has" is singular and correct for the subject. However, "assign" is the base form, not the past participle needed for the passive voice and the present perfect tense. The past participle is "assigned". Incorrect.
4. no improvement: The original phrase "has been assigned" correctly uses the singular auxiliary "has" with the passive and present perfect structure ("been assigned") to agree with the singular subject "a person".

Based on the analysis, the original phrase "(has been assigned)" is grammatically correct for the singular subject "a person" in the present perfect passive voice. Therefore, no improvement is needed.

Revision Table: Subject-Verb Agreement and Passive Voice

Additional Information on Passive Voice

The passive voice is used when the action is more important than the doer, or when the doer is unknown or obvious. The structure is typically Subject + form of 'be' + Past Participle.

• Simple Present Passive: is/am/are + past participle (e.g., The trees are watered daily.)
• Simple Past Passive: was/were + past participle (e.g., The duty was assigned yesterday.)
• Present Continuous Passive: is/am/are being + past participle (e.g., The trees are being planted now.)
• Past Continuous Passive: was/were being + past participle (e.g., The duty was being assigned when I arrived.)
• Past Perfect Passive: had been + past participle (e.g., The duty had been assigned before the project started.)
• Future Simple Passive: will be + past participle (e.g., The duty will be assigned tomorrow.)

Understanding the correct auxiliary verbs (like 'has' vs 'have') and the requirement for the past participle in passive constructions is crucial for sentence improvement tasks.