Several months ago, Fiat Chrysler CEO Sergio Marchionne sent Barra an email saying he wanted the two companies to merge, a notion Barra has consistently said she and the company's board of directors are not interested in.
Take context from the input text and decide on the accurate relationship between 'Sergio Marchionne' and 'Fiat' from the options provided.
Options: parent organization, operator, employer, platform