02·Filtering, sorting, missing data

What does df["category"].replace({"A": 1, "B": 2, "C": 3}) do?

• Raises an error for values outside the dictionary.
• Maps Series values via a dictionary — A→1, B→2, C→3. Values outside the dict stay unchanged. Also works with lists: replace([1, 2], [10, 20]).
• Drops rows with values A, B, C.
• Renames the category column.