Answer:
"Why should the forest be preserved by us?"
Step-by-step explanation:
An active voice is when the speech of a person is written or said as it is, with no change. But a passive voice is when the speech is reported to another person with some changes in structure but still retains the same meaning.
In the given active voice question, "Why should we preserve the Forest?", the question tag "why" will remain in the same place. Question tags such as why, who, what, how, etc. remain unchanged in their position in a passive voice. After that, the subject moves to the end of the sentence while the object moves to the subject's position in the sentence. And "we" will be changed into "us".
Thus, the final answer is- "Why should the forest be preserved by us?"