At the bottom of the world lies a mighty continent still wrapped in the Ice Age and, until recent times, unknown to man. It is a great land mass crisscrossed (交叉往来) by mountain ranges whose【C1】______ and height are still uncertain. Much of the continent is a complete blank on our maps. A 1 000-mile【C2】______ of the coastline has never been【C3】______ by any ship. Man has【C4】______ , on foot, less than one percent of its area. Antarctica differs slightly【C5】______ the Arctic regions. The Arctic is an ocean, covered with【C6】______ packed ice and surrounded by the land masses of Europe, Asia, and North America. The Antarctic is a continent 【C7】______ as large as Europe and Australia 【C8】______ , centered roughly on the South Pole and surrounded by the most【C9】______ water areas of the world—the Atlantic, Pacific and Indian Ocean. The continental ice pack is more than two【C10】______ high at its center thus, the air over the Antarctic is far more refrigerated (冰冻的) than it is over the Arctic regions. This cold air falls 【C11】______the land with such force that it 【C12】______ the nearby seas the stormiest in the world and renders【C13】______ those regions whose【C14】______ at the opposite end of the globe are inhabited.【C15】______ , more than a million persons live【C16】______ 2 000 miles of the North Pole in an area that【C17】______ most of Alaska, Siberia, and Scandinavia a【C18】______ rich in forest and mining industries. Except for a handful of【C19】 ______ stations, within the same distance of the South Pole there is not a(an)【C20】______ tree, industry, or settlement. 【C1】