To print "Unavailable," the program must trap the specific error raised by the try block. Accessing a non-existent key ("calzone") in a dictionary raises a KeyError. Therefore, the first box must contain except KeyError: to catch this specific exception and execute the immediate indented command print("Unavailable").

The second box requires a valid statement that accepts an indented block to maintain syntax validity. except: is the correct choice here, serving as a catch-all handler for any other exceptions. While it will not execute in this scenario (as the error is already caught), it is structurally required for the subsequent print("Out of bounds"). The pass statement is incorrect because it does not accept an indented block, which would cause an IndentationError.

Python Software Foundation. (n.d.). Errors and Exceptions - 8.3 Handling Exceptions. Python 3 Documentation. Retrieved from https://docs.python.org/3/tutorial/errors.html#handling-exceptions

Reference confirms the syntax for try...except blocks and that a class-based exception (like KeyError) matches if it is the same class or a base class.

Python Software Foundation. (n.d.). Built-in Exceptions - KeyError. Python 3 Documentation. Retrieved from https://docs.python.org/3/library/exceptions.html#KeyError

Reference confirms that a KeyError is raised when a mapping (dictionary) key is not found in the set of existing keys.

Python Software Foundation. (n.d.). Simple Statements - The pass statement. Python 3 Documentation. Retrieved from https://docs.python.org/3/reference/simple_stmts.html#the-pass-statement

Reference confirms pass is a null operation used when a statement is required syntactically but no code needs to be executed; it does not introduce a new indented block.