What is the correct syntax to add a new key-value pair to a dictionary?

To add a new key-value pair to a dictionary in Python, you can use the syntax where you specify the key in square brackets and assign the desired value to it, as demonstrated in the choice where the dictionary name is followed by indexing syntax: dictionary_name["key"] = "value".

In this approach, if the key does not already exist in the dictionary, it is created with the specified value. If the key already exists, the associated value is updated. This functionality allows for dynamic manipulation of data stored within dictionaries, making it a flexible and widely-used feature in Python programming.

The other choices do not provide valid methods for adding key-value pairs in a dictionary. For example, using the method add is not applicable to dictionaries; it's a common method for sets. The method insert does not exist for dictionaries; it's related to list operations. Likewise, the method put is not a part of Python's native dictionary methods and might be associated with other programming languages or data structures.