Correct Answer: The baby is loved by the mother.

Solution : The fourth option is the correct choice.

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: "Singular object + is + past participle form of the verb + 'by' followed by the agent of the action."

Therefore, the correct answer is: The baby is loved by the mother.