The total area of land on earth is about 149 million square kilometers, or about 39 percent of the total area of the earth.          The average height of the land is about 750 metres above the sea level .The Eurasian land mass is the largest with an area of 54,527,600 square kilometers .The smallest continent is the Australian mainland, with an area of about 7,614,600 square kilometers, which together with Tasmania, New Zealand, New Guinea and the Pacific Islands, is described as Oceania .The total area of Oceania is about 8,935,500 square kilometres, including West Iran which is political in Asia .          The world's largest peninsula is Arabia ,with an area of about 3,327,500 square kilometres .          The largest island in the world is Greenland, with an area of about 2,175,600 square kilometres. The largest island surrounded by fresh water is the Ilha de Marajo (4,022 square kilometres) in the mouth of the Amazon River, Brazil .The largest island in a lake is Manitoulin Island (2,766 square kilometres) in the Canadian section of Lake Huron . This island itself has on it a lake of 106 square kilometres called Manitou lake, in which there are several islands. The largest island surrounded by fresh water is in    _  .
a river a lake a sea an ocean
Question: The total area of land on earth is about 149 million square kilometers, or about 39 percent of the total area of the earth.          The average height of the land is about 750 metres above the sea level .The Eurasian land mass is the largest with an area of 54,527,600 square kilometers .The smallest continent is the Australian mainland, with an area of about 7,614,600 square kilometers, which together with Tasmania, New Zealand, New Guinea and the Pacific Islands, is described as Oceania .The total area of Oceania is about 8,935,500 square kilometres, including West Iran which is political in Asia .          The world's largest peninsula is Arabia ,with an area of about 3,327,500 square kilometres .          The largest island in the world is Greenland, with an area of about 2,175,600 square kilometres. The largest island surrounded by fresh water is the Ilha de Marajo (4,022 square kilometres) in the mouth of the Amazon River, Brazil .The largest island in a lake is Manitoulin Island (2,766 square kilometres) in the Canadian section of Lake Huron . This island itself has on it a lake of 106 square kilometres called Manitou lake, in which there are several islands. The largest island surrounded by fresh water is in    _  .
A. a river
B. a lake
C. a sea
D. an ocean
Answer: