Option B (Arctic Ocean) is the correct answer. The context mentions that geographers have divided the oceanic part of the earth into five oceans: the Pacific, the Atlantic, the Indian, Southern ocean and the Arctic. Among these five oceans, the Arctic Ocean is the smallest in size. This is a fundamental fact about ocean geography covered in NCERT textbooks. The Pacific Ocean is the largest, followed by the Atlantic, Indian, Southern, and finally the Arctic Ocean as the smallest.