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

Their behaviour vexes us.

We are vexed by their behaviour.

The correct option that expresses the given sentence in passive voice is We are vexed by their behaviour.

The other options are incorrect because:

• Their behaviour vexes us is in the active voice.
• We had been vexed by their behaviour is in the past perfect tense, while the original sentence is in the present tense.
• We have been vexed by their behaviour is also in the past perfect tense.
• We are being vexed by their behaviour is in the present progressive tense.