1. To what extent is the nuclear risk acceptable?

2. The nuclear risk is acceptable ___ ______. [the structure is preposition + noun phrase]

[Which words can we put in the two blanks?]

I'd turn #2 into a question: To what extent is the nuclear risk acceptable?

I can't think of a way to make #2 a smooth indicative sentence.

Or is #2 supposed to be a way to answer #1?