Select the option that expresses the given sentence in passive voice.

somebody is following us.

We're being followed by somebody.

The correct passive voice of the given sentence somebody is following us is We're being followed by somebody.

The active voice of the sentence is somebody is following us. This sentence is in the present continuous tense, which is used to describe an action that is happening now. The passive voice of the sentence is formed by putting the subject of the active sentence after the verb "to be" and the present participle of the main verb. In this case, the subject of the active sentence is "us" and the main verb is "follow." The present participle of "follow" is "following." So, the passive form of the sentence is We're being followed by somebody.

The other options are incorrect because:

• Somebody had been following us. is in the past perfect tense, which is used to describe an action that happened in the past before another action happened. There is no other action mentioned in the sentence, so the past perfect tense is not appropriate.
• We have been following by somebody. is grammatically incorrect. The correct preposition to use after the verb "to be" in the passive voice is "by."
• Somebody is following us. is in the active voice, not the passive voice.