(D) A daily wage labourer working under a contractor.
The unorganised sector has no job security, no fixed wages, and no government-regulated employment terms — all of which apply to a daily wage labourer.
Options A, B, and C involve schools, big factories, and hospitals — all registered, regulated organisations belonging to the organised sector. The unorganised sector is characterised by irregular, low-paid work with no legal protection, exactly matching a daily wage labourer under a contractor. Examiners expect the correct option plus a brief reason.