In the 1800s, who were referred to as the dikus?

Moneylenders

The correct answer is Option (3) → Moneylenders

NCERT-"When the Santhals settled on the peripheries of the Rajmahal hills, the Paharias resisted but were ultimately forced to withdraw deeper into the hills. Restricted from moving down to the lower hills and valleys, they were confined to the dry interior and to the more barren and rocky upper hills. This severely affected their lives, impoverishing them in the long term. Shifting agriculture depended on the ability to move to newer and newer land and utilisation of the natural fertility of the soil. When the most fertile soils became inaccessible to them, being part of the Damin, the Paharias could not effectively sustain their mode of cultivation. When the forests of the region were cleared for cultivation the hunters amongst them also faced problems. The Santhals, by contrast, gave up their earlier life of mobility and settled down, cultivating a range of commercial crops for the market, and dealing with traders and moneylenders.  The Santhals, however, soon found that the land they had brought under cultivation was slipping away from their hands. The state was levying heavy taxes on the land that the Santhals had cleared, moneylenders (dikus) were charging them high rates of interest and taking over the land when debts remained unpaid, and zamindars were asserting control over the Damin area."

Note: As per NCERT, only moneylenders has been referred to as "dikus". However, in the 1800s, the Santhals used the word “dikus” to refer to outsiders such as merchants, moneylenders, zamindars, and British officials. These people exploited the Santhals by taking their land, charging heavy interest, and making them suffer. Thus, merchants could also be the answer of this question.