A. Dictionary keys must be mutable
B. Dictionary values must be immutable
C. Dictionary reserves insertion order only in Python 2
D. Dictionary keys must be unique

Solution

D. Dictionary keys must be unique

Explanation

A dictionary cannot contain duplicate keys; a later value for the same key replaces the earlier one.

Dictionary में duplicate keys नहीं हो सकतीं; same key की नई value पुरानी value को replace करती है।