Option 1, the Polynesia, is incorrect. Polynesia refers to a different region in the Pacific, which includes islands such as Hawaii, Samoa, Tonga, and French Polynesia. It is located further east of Melanesia.

Option 2, the Melanesia, is the correct answer. Melanesia refers to the region in the Pacific that includes the Pacific Islands from New Guinea southeastwards to the Fiji Islands group. The term Melanesia comes from the Greek words "melas" meaning black and "nesos" meaning island, referring to the darker-skinned populations found in this region.

Option 3, the Micronesia, is incorrect. Micronesia is a different region in the Pacific, consisting of small islands located north of Melanesia.

Option 4, the Australasia, is incorrect. Australasia refers to a different geographical region that includes Australia, New Zealand, Papua New Guinea, and some neighboring islands. It does not specifically refer to the Pacific Islands from New Guinea southeastwards to the Fiji Islands group.

Therefore, the correct answer is option 2, the Melanesia.