Question

Change the following sentence into a passive voice.
The smoke of the factory had polluted the fresh air.

a)The fresh air had polluted the smoke of the factory.
b)The fresh air had been polluted by the smoke of the factory.
c)The fresh air had been polluted with the smoke of the factory.
d)None of the above.

Answer 1

Hint: If a sentence is in the active voice, it stresses on the subject doing an action. If the sentence is in the passive voice, the emphasis is laid on the action being done by the subject or on the object of the sentence.

Complete step-by-step answer:

 In the given sentence, the subject is ‘the smoke of the factory’ while the action being done by the subject is to ‘pollute the fresh air’. The object is the ‘fresh air’. To change it into a passive voice, we have to lay emphasis on the action being done by the object. Therefore, we have to bring the object to the beginning of the sentence. However, we see that options a, b and c start with the object ‘fresh air’. In passive voice, an action is always done ‘by’ someone or something. Thus, option b is correct.
Option a is wrong because the sentence conveys a totally different meaning than the one intended. It says that the fresh air was responsible for polluting the smoke of the factory when it was actually the smoke of the factory which polluted the fresh air.
In option c, though the emphasis is on the object of the sentence, the usage of the preposition ‘with’ is incorrect. Thus, option c is wrong.
Option d, that is, ‘None of these’ is to confuse you that none of the given sentences is correct.

Note: Always bringing the object of the sentence to the beginning of the sentence does not change it into a passive voice. For example, the sentence ‘Harry gave some flowers to Ginny’ can be changed into two passive voice sentences: ‘Some flowers were given to Ginny by Harry’ and ‘Ginny was given some flowers by Harry’. So the more dependable rule is that the action is emphasized and not that the object is brought to the beginning of the sentence.