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

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