1.'More than ten times' is just an expression of quantity and not a comparator. The comparator is actually the positive degree ‘as much’. Now when the un-underlined portion contains ‘as much’ for the comparison, then you must idiomatically complete the comparison with another ‘as’. This means, we have to stay put with choices B, C and D, dropping A and E.
2.We must not misconstrue that the pronoun ‘it’ stands for just energy, The pronoun stands for the entire antecedent that goes to describe the energy namely ‘more than ten times as much energy’; Therefore the use of the pronoun ‘it’ doesn’t make much structural sense. We have to drop choices B and D on that count. We must admit C as the most fitting, though a bit unusual to the ears.
Incidentally a colon is no more than a kind of parenthesis. The things that follow the colon must represent the idea that is expressed prior to the colon, in this case ‘hopeful signs that we are shifting away from our heavy reliance on fossil fuels;
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