正解:A
The code defines a function get_credentials() which returns a dictionary containing a username and password.
When the function is called, it retrieves the value associated with the key 'username' from this dictionary.
Since the value for 'username' is set to 'Cisco', the output of this code when the print(get_credentials()) statement is executed will be 'Cisco'.
References: This explanation is based on general programming knowledge in Python, as specific references to Implementing and Operating Cisco Service Provider Network Core Technologies (SPCOR)