In 1698, Fort William was established by the Hoogly river by Britishers for which purpose?

defensive purposes

The correct answer is option 3: defensive purposes

NCERT: In 1690, an English merchant named Job Charnock arranged to lease three villages (named Kolikata, Gobindapur, and Sutanuti) by the river Hugli in order to set up a trading post. In 1698, Fort William was established by the river for defensive purposes, and a large open area was cleared around the fort for military engagements. The fort and the open area (called Maidan) formed the core of the city that emerged rather rapidly.