Take context from the input text and decide on the accurate relationship between 'Mary Barra' and 'General Motors' from the options provided.
Options: operator, director/manager, employer, brand

The most improved brand is General Motors (NYSE: GM ) ("CEO Mary Barra has made it her goal to ... make sure errors of the past are not forgotten and not repeated"), followed by Target (NYSE: TGT ), travel website Trivago and GM brands Chevrolet and Buick.
employer