单项选择题

Water
From the beginning, water has furnished man with a source of food and a highway to travel upon. The first 16 arose where water was a dominant element in the environment, a challenge to man"s ingenuity.
The Egyptians invented the 365-day calendar 17 the Nile"s annual flooding. The Babylonians, who were among the most famous law-makers in ancient times, invented laws 18 water usage. Water inspired the Chinese to build a 1,000- 19 canal, a complex system which, after nearly 2,500 years, remains still practically 20 and still commands the astonishment of engineer.
But the 21 never found complete solutions to their water problems. The Yellow River is also known 22 "China"s Sorrow"; it is so unpredictable and dangerous 23 in a single flood it has caused a million 24 . Floods slowed the great civilization of the Indus River Valley, and inadequate drainage ruined 25 of its land.
Today water dominates 26 as it always has done. Its presence continues to 27 the location of his homes and cities; its violent variability can 28 man of his herds or his crops; its routes links him 29 his fellows; its immense value may 30 to already dangerous political conflicts. There are many examples of this in our own time.

A.increase
B.add
C.expand
D.extend
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