Hi,
I agree that option C is the best of all.But doesn't "increased sufficiently...to begin" sound strange?
It seems the intention of such increase is to begin something.

Option D falling employment rates that are triggered[/b] by a drop in investment, causing people to cut consumer spending and starting a cycle of layoffs that lead back to even lower employment rates. aaa, I tend to agree with Guest79 - the first "that" is awkward and unnecessary; -dan cou...