In the context of the input sentence, determine the relationship between 'Mary Barra' and 'General Motors'.
Options: operator, employer, brand, director/manager

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