阅读下面短文,在空白处填入1个适当的单词或括号内单词的正确形式。

As the economy flourishes (v. 繁荣), there always comes a time 【小题1】 the old must give way to the new, and thus it is not likely 【小题2】 (preserve) everything from the past. In this case, keeping the right balance between progress and the【小题3】 (protect) of cultural heritage sites can be 【小题4】 big challenge.

       In 1902, a dam was completed at Aswan, which provided irrigation (n. 灌溉) during 【小题5】 (dry) but could not hold back the annual flood of the mighty (adj. 浩荡的；巨大的) Nile River. In the 1950s, the Egyptian government proposed that a new dam【小题6】 (build) across the Nile 【小题7】 (benefit) more farmers. 【小题8】, the proposal led to protests because water from the dam would likely【小题9】 (threat) a number of cultural relics of unique historical 【小题10】 (significant) to Egypt.