An engineer implements a Python script inside a Cisco Bash shell. The script contains this dictionary object: Which command must be used to add the 'NSK-Spine-2': `1498323434' element to the…

The `+=` operator is not used for merging dictionaries in this manner; it typically performs in-place addition for lists or concatenation for strings, and would result in a TypeError for dictionaries.

Assigning a new dictionary using `=` would overwrite the existing `switch_id_list` dictionary, not add an element to it, and the syntax `["N9K-Spine-2": "1498323434"]` is incorrect for creating a dictionary.

The `append()` method is used to add an item to the end of a list, not to merge elements into a dictionary. If `switch_id_list` were a list, `append` would be applicable, but the question states it's a dictionary object.

In Python, the `update()` method is used to add items from another dictionary (or an iterable of key-value pairs) to the current dictionary. It efficiently merges the new dictionary `{'N9K-Spine-2': '1498323434'}` into `switch_id_list`, adding the new key-value pair as required.