An office management company has a head office in Nova Scotia with $150$ employees, but also has $50$ employees in a branch office in British Columbia and $300$ employees in a branch office in Alberta. What provincial employment standards acts should the HR department follow?

A$.$ the ESA of Nova Scotia, since the head office is there

B$.$ the ESA of Alberta, since most employees are there

C$.$ the ESA of Alberta, Nova Scotia, or British Columbia, depending on where the employee works

D$.$ the federal ESA, since they have employees across Canada