Explanation:

- Option 1: a - "Her impudent behavior" is grammatically correct. It begins the sentence by identifying whose behavior is being discussed.

- Option 2: b - "was completely inappropriate for such" is also correct. It describes the behavior as inappropriate for the situation.

- Option 3: c - "a formal occasion." correctly concludes the sentence, specifying the context of the behavior.

- Option 4: d - "No error" is the given option if the sentence is considered grammatically correct as it stands.

Correct Answer: Option 4: d

.