慢速英语:Hoover Dam: Taming the Colorado River and Providing Electricity to Millions

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a great deal of大量的

例句：He talked a great deal of sense.
      他讲得很有道理。

2.Today this is no longer true. Taller dams, larger dams and a few that produce more power have been created.

no longer不再, 已不, 不复, 再也不

例句：He was long a famous musician, but he plays no longer.
      他成为有名的音乐家已很久了, 但他现在不演奏了。

      The city's water supply is no longer adequate for its need.
      这个城市的供水已不敷需求。

3.The new bridge keeps the majority of vehicles further away from the dam.

keep away from(使)不接近

例句：Keep away from the furnace.
      不要靠近炉子。

      Keep the children away from the machine.
      别让孩子们接近机器。