His behaviour surprised us.

We were surprised at his behaviour

We are surprised at his behaviour

We will be surprised at his behaviour

We shall surprised at his behaviour

All of the above

Surprise is a verb which means حیران رہ جانا

We use at after surprise.

Past Indefinite tense

Active Voice= Subject + Second Form of Verb + Object (His behaviour surprised us)

Passive Voice = Object + was/were + third of verb + by + subject (We were surprised at his behaviour)