Answer:
The correct answer is option C.
Step-by-step explanation:
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Let's solve this!
We will analyze each of the options:
They provide water for the irrigation of crop: this is a benefit for humanity, so it is not a problem
They collect and store water for human use: water is used for irrigation, and for some other use that is needed.
They impede fish migration and spawning: for example it is the case of salmon, this is a big problem of dams.
They can be used to generate electricity: this option is incorrect because it is one of the biggest benefits of dams.
After the analysis, we conclude that the problem of the dams and therefore, the correct answer is option C.