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 by mountain(51) whose extent and elevation are still uncertain. Much of the(52)is a complete blank on our maps. A 1,000-mile stretch of the coastline has never been(53)by any ship. Man has(54), on foot, less than one per cent of its ares.

Antarctica differs fundamentally from the Arctic regions. The Arctic is an ocean,(55)with drifting packed ice and surrounded by the land masses of Europe, Asia, and North America. The Antarctic is a continent nearly as(56)as Europe and Au stralia combined, centered roughly(57)the South Pole and(58)by the most unobstructed water areas of the world—the Atlantic, Pacific, and Indian Oceans.

The continental ice(59)is more than two miles high at its center; thus, the air over the Antarctic is far more refrigerated than it is over the Arctic regions. This(60)air cascades off the land with such(61)that it makes the nearby seas the stormiest in the world and renders(62)those regions whose counterparts at the opposite end of the(63)are inhabited. Thus, more than a million persons live within 2,000 miles of the North Pole in an area that(64)most of Alaska, Siberia, and Scandenavia—a region(65)in forest and mining industries. Except for a handful of weather stations, within the same distance of the South Pole there is not a single tree, industry, or settlement.

A．valleys

B．villages

C．paths

D．ranges