Questions below refer to the following article.
The Tei Kai region is famous for its towering mountains to the north, and its desert plains to the south. Long known as a dry and barren region, it has undergone a transformation (1)............... the last fifty years.
During this time, visitors (2)............... a major change in the landscape. The construction of the Wan Hei dam enabled engineers to channel the waters of the Gang River for agricultural purposes. The result has been a narrow but expanding corridor of greenery spreading (3)............... the once barren land. There has also been a subsequent rise in the population and wealth of the region.