V. Fill in each blank space with one appropriate from the box. .
The Great Wall is probably China's best-known monument and one of its (26) popular tourist destinations. In 1987 it was designated a World Heritage Site by the United Nations Educational, Scientific and Cultural Organization (UNESCO). The Great Wall is not a (27) , continuous structure. Rather, it consists of a network of walls and towers that leaves the frontier open in places. Estimates of the total length of the monument vary, depending on (28) sections are included and how they are measured. The Great Wall is about 2,400 km (about 1,500 miles) long, (29) conservative estimates. Other estimates cite a length of 6,400 km (4,000 miles), or even longer. Some long-standing myths about the wall have been dispelled in recent decades. The existing wall is not several thousand years old, nor is it, as has been widely asserted, visible with the (30)______ eye from outer space. (Astronauts have confirmed this. However, same of the wall is discernible in special radar images taken by satellites.)
(26)
A.more
B.most
C.less
D.so