Which line must be added in the Python function to return the JSON object {`cat_9k`: `FXS1932Q2SE`}?

Which line must be added in the Python function to return the JSON object {`cat_9k`: `FXS1932Q2SE`}?

A. return (json.dumps({d['hostname']: d['serialNumber'] for d in json.loads(test_json)['response']})) B. return (json.dumps({for d in json.loads(test_json)['response']: d['hostname']: d['serialNumber']})) C. return (json.loads({d['hostname']: d['serialNumber'] for d in json.dumps(test_json)['response'})) D. return (json.loads({for d in json.dumps(test_json)['response']: d['hostname']: d['serialNumber']}))