Correct Answer: New nests are built by swallows every year.

Solution : The correct choice is the second 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 voice becomes the subject in the passive voice.

The structure of the passive voice in the case of the simple present tense is: " Plural object + are + past participle form of the verb + 'by' followed by the agent of the action ."

Therefore, the sentence in passive form is: New nests are built by swallows every year.