Explanation:

No source of energy can be called pollution-free, because, the use of any source of energy disturbs the environment in one way or the other. A source of energy like a solar cell is pollution free in actual operation but the assembly of the device might have caused some damage to the environment

The efficiency of power plants based on wave energy is very low. Moreover, the power plants built in oceans or at sea-shores have high cost of installation, corrode easily and need a lot of maintenance.

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Answer:

No source of energy can be pollution free because even if it is clean, its assembly could have caused some environmental damage. Hydrogen has been used as rocket fuel. ... The carbon dioxide can produce greenhouse effect in the atmosphere and lead to the excessive heating of the environment in long run.