Correct Answer: The residents of the slum were woken up by the barking of dogs.

Solution : The correct choice is the fourth option.

Passive voice is the voice in which the object experiences an action rather than the person who performs the action. Hence, the object in the active sentence becomes the subject in the passive voice.

This construction follows the standard structure of passive voice, where the receiver of the action (the residents) comes first, followed by the auxiliary verb "were" and the past participle "woken up".

The structure of the passive voice sentence used here is: subject ("The residents of the slum") + verb ("were woken up") + past participle of the main verb ("woken") + by + agent ("the barking of dogs").

Therefore, the correct answer is: The residents of the slum were woken up by the barking of dogs.