Answer:
The sentence in an active tone is:
"The prisoner is not being guarded."
Explanation:
In active voice, the sentence is rewritten to show that the guards are not actively guarding the prisoner, which is very dangerous.
What are Active Voices?
Active voice is a grammatical voice in which the subject of the sentence performs the action mentioned by the verb. In active voice, the subject is the doer of the action.
For example, in the sentence "The cat chased the mouse," "the cat" is the subject and it is performing the action, Which is chasing the mouse.