The argument made in the text is that “no new nuclear plants..they will not be needed”.
We must find a reason why not building new nuclear power plants could prove to be unsafe.
1 – Correct
If the demand for electricity goes up, new nuclear power plants would be needed.
2 – Correct
If the green technologies start to become inefficient in producing electricity, then new nuclear plants will be needed.
3 – Wrong
Storing nuclear waste is irrelevant to the argument and to the question.
Since statements 1 and 2 are correct, C is the answer.