The first is a generalization [Most government agencies become less effective over time]
The generalization is used as the basis for an opinion [recommend that every agency be eliminated after 10 years and created anew by replacing...]
That opinion is rejected by the analyst [However, this policy would be impractical since]
The second is a consideration used to defend the analyst's position.
Upon first reading, I had picked B as well. In fact D sounded very convoluted as I was reading this question by putting a time constraint in my head.
I agree with D and Artemov's analysis.