What is the difference between a shallow copy and a deep copy?

A shallow copy creates a new object, but instead of copying the elements themselves, it only copies references to those elements from the original object. This means that if the object contains nested structures like lists or dictionaries, the shallow copy reflects changes made to those nested structures since both the original and the shallow copy point to the same objects in memory.

In contrast, a deep copy duplicates both the object and all objects nested within it, creating entirely new instances of the nested objects. This ensures that modifications to the copied object do not affect the original object. The statement about a shallow copy refers specifically to the copying mechanism—making it essential for understanding how changes to the original and copied objects can influence each other.

The other choices incorrectly describe the behaviors of shallow and deep copies. For instance, deep copies do copy nested objects, and they do so in a manner that they are independent of the original objects. Furthermore, the notion that deep copies only copy basic data types misrepresents what a deep copy does, as it applies to all nested objects regardless of their type.