Understanding Active and Passive Voice Transformation

The question asks us to convert a sentence from active voice to passive voice. The original sentence is: "The police beat a number of protestors last night."

In the active voice, the subject performs the action. In the passive voice, the action is performed on the subject (which was the object in the active sentence).

Let's identify the components of the active sentence:

• Subject: The police
• Verb: beat
• Object: a number of protestors
• Time Expression: last night

The verb 'beat' in this sentence is in the simple past tense. To convert a simple past active sentence into passive voice, we follow this structure:

\(\text{Object} + \text{was/were} + \text{Past Participle of the verb} + (\text{by} + \text{Subject}) + \text{Time Expression}\)

Applying this rule to our sentence:

• The object is "a number of protestors". Since 'a number of protestors' is plural, we use 'were'.
• The past participle of 'beat' is 'beaten'.
• The original subject was "The police", so we add "by the police".
• The time expression "last night" remains the same.

Putting it all together, the passive voice sentence is: "A number of protestors were beaten by the police last night."

Evaluating the Options for Passive Voice

Let's examine each option provided:

1. A number of protestors had been beaten by the police last night.
   This uses the past perfect passive tense (had been beaten). This is incorrect as the original sentence is in simple past tense.
2. A number of protestors were being beaten by the police last night.
   This uses the past continuous passive tense (were being beaten). This is incorrect as the original sentence is in simple past tense.
3. A number of protestors has been beaten by the police the night before.
   This uses the present perfect passive tense (has been beaten) and also changes the time expression ('last night' to 'the night before'), which is unnecessary and alters the meaning slightly depending on context. This is incorrect.
4. A number of protestors were beaten by the police last night.
   This uses the correct structure for the simple past passive tense (were + beaten) and retains the correct time expression. This matches our derived passive sentence.

Therefore, option 4 is the correct passive form of the given sentence.

Revision Table: Simple Past Active vs. Passive Voice

Additional Information on Passive Voice Usage

The passive voice is often used when:

• The doer of the action is unknown, unimportant, or obvious from the context.
• We want to emphasize the action itself or the receiver of the action rather than the doer.
• Reporting news or scientific findings, where the process or result is more important than who did it.

In the given sentence, converting it to passive voice shifts the focus from 'The police' (the doer) to 'a number of protestors' (the receiver of the action), which might be useful depending on the context or what you want to highlight.