Answers

2014-06-27T20:44:37+05:30
The disadvantages is that canals require significant manpower to build and maintain (very costly) and boats travel slowly. They also only work in areas that are reasonably flat. They are also susceptible to flooding, droughts, freezing, and other natural occurrences.
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2014-06-27T21:51:15+05:30
They  work in areas that are reasonably flat. They are also susceptible to flooding, droughts, freezing, and other natural occurrences.
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