Understanding Active and Passive Voice

In English grammar, voice refers to the form of a verb that shows whether the subject of the sentence performs the action (active voice) or is acted upon (passive voice).

• Active Voice: The subject performs the action. Structure is typically Subject + Verb + Object.
• Passive Voice: The subject receives the action. Structure is typically Object + Be (appropriate form) + Past Participle + by + Subject (optional).

Analyzing the Given Sentence

The sentence provided is: "The teacher is explaining the lesson."

• Subject: The teacher (performing the action)
• Verb: is explaining (present continuous tense)
• Object: the lesson (receiving the action)

Since the subject ("The teacher") is performing the action ("is explaining"), this sentence is in the active voice and specifically in the present continuous tense.

Converting Present Continuous Active to Passive Voice

To change a sentence from active voice in the present continuous tense to passive voice, we follow a specific structure:

Let's apply this rule to our sentence "The teacher is explaining the lesson."

1. Identify the Object of the active sentence: "the lesson". This becomes the Subject of the passive sentence.
2. Identify the Verb: "is explaining". The tense is present continuous.
3. Use the appropriate form of 'be' + 'being' + Past Participle. Since the new subject ("The lesson") is singular, we use "is". The past participle of "explaining" is "explained". So, we get "is being explained".
4. Identify the Subject of the active sentence: "The teacher". This becomes the object of the passive sentence, preceded by "by". So, "by the teacher".

Combining these parts, the passive voice sentence is: "The lesson is being explained by the teacher."

Evaluating the Options

Let's look at the given options and see which one matches our derived passive voice sentence:

1. The lesson explained the teacher.

   This sentence is active voice (Subject: The lesson, Verb: explained) and changes the meaning entirely. Incorrect.

2. The teacher explained the lesson.

   This sentence is active voice and in the simple past tense. The original sentence was present continuous active. Incorrect.

3. The lesson is being explained by the teacher.

   This sentence matches the structure we derived for the passive voice of a present continuous sentence (Subject: The lesson, Verb: is being explained, by + Object: by the teacher). Correct.

4. The lesson was explained by the teacher.

   This sentence is passive voice but in the simple past tense ("was explained"). The original sentence was present continuous. Incorrect.

Conclusion

Based on the rules for converting present continuous active voice to passive voice, the correct transformation of the sentence "The teacher is explaining the lesson" is "The lesson is being explained by the teacher."

Revision Table: Voice Change Summary

Additional Information on Passive Voice

Passive voice is often used:

• When the doer of the action (the agent) is unknown, unimportant, or obvious from the context. Example: "The window was broken." (We don't know or care who broke it).
• When the action itself is more important than the doer. Example: "The new policy was announced yesterday." (The announcement is the key event).
• In scientific or technical writing to maintain objectivity. Example: "The samples were heated to 100°C."
• To avoid mentioning who is responsible for something. Example: "Mistakes were made."

While passive voice is useful, overuse can make writing sound awkward or unclear. Active voice is generally more direct and energetic.