Step 1: Understanding Prepositions of Reaction:
The correct preposition following "surprised" when referring to an action or event is "to." We say "surprised to hear" when describing someone's reaction to something. Step 2: Analyzing the Options:
- By: This is incorrect because "by" is used to indicate the agent causing the surprise, not the event.
- To: The correct preposition when describing a reaction to something, such as being surprised "to hear" something.
- At: This is incorrect because "at" is used for physical locations or directions, not for reactions.
- Of: This is incorrect because "of" is used with different verbs, not "surprised." Step 3: Conclusion:
The correct preposition is to, as it fits the context of being surprised by an action.