The correct answer is: D. No error
The sentence is grammatically correct. The word “pleased” is an adjective that describes the subject of the sentence, “I.” The word “to know that” is an infinitive phrase that functions as the object of the preposition “pleased.” The word “you” is the subject of the verb phrase “have topped the list.” The word “list” is the object of the verb “topped.”
The sentence is clear and easy to understand. It conveys the message that the speaker is happy to know that the listener has topped the list.