Which of the following statements is true about Python dictionaries?

In Python dictionaries, the statement that keys must be unique within a dictionary is indeed true. Each key in a dictionary serves as an identifier for its corresponding value, and because of this, no two keys can be the same. If you attempt to assign a value to a key that already exists in the dictionary, the previous value for that key will be overwritten with the new value. This uniqueness is essential for maintaining the integrity of the mapping between keys and their respective values.

On the other hand, dictionaries do allow for various types of values, meaning that different keys can have values of differing types. Additionally, while dictionaries in Python versions 3.7 and later maintain the order of entries based on their insertion order, this characteristic is not a requirement of dictionaries as defined in earlier versions or as per the language's specifications. Furthermore, there is no limitation that constrains dictionary keys to only being strings; keys can be of various immutable types, including integers, tuples, and more.