Final answer:
Hamlet thought it was a nobleman hiding behind the curtain. This implies that Hamlet believed he was attacking someone of higher status or nobility, rather than a lesser figure like a messenger, spy, or ghost
Step-by-step explanation:
Based on the given information, Hamlet says 'I took thee [Polonius] for thy better,' which indicates that Hamlet thought it was a nobleman hiding behind the curtain.
This implies that Hamlet believed he was attacking someone of higher status or nobility, rather than a lesser figure like a messenger, spy, or ghost