(c) Engineer, Professor, Farmer
Engineer and Professor belong to the secondary and tertiary sectors respectively, but Farmer belongs to the primary sector, making it the odd one out. The other options (a), (b), (d) contain workers from mixed or same sectors consistently.
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The question tests knowledge of sectoral classification. A Farmer is a primary sector worker; an Engineer (secondary) and Professor (tertiary) are from different sectors—but the key point is that in options (a), (b), and (d), all workers listed belong to the tertiary (service) sector (pilots, drivers, gardeners provide services; teachers, lawyers, doctors are service workers). Only option (c) breaks this pattern by including a primary sector worker (Farmer) among secondary/tertiary workers, making it the odd one out.