All bridges built from 1950 to 1960 are in need of serious rehab, but we don't know for sure that suspension bridges are among any of the bridges built during that period. It could be that during those ten years, no suspension bridges were built at all.

Here's the January powerscore podcast:

A: Should adopt measure → measure is required to solve a problem

C: measure is required to solve a problem → should adopt measure

How do we support the politician's argument? We need to bridge the gap between the premise (increasing taxation is a required measure for government intervention) and the conclusion (we should raise taxes).

C works because it maps the premise and conclusion onto the sufficient and necessary assumptions respectively. If the SA is valid, the necessary assumption follows.

In A, we see that the conclusion is mapped onto the sufficient assumption, and the premise onto NA. That's not good, because we cannot conclude from the validity of the NA that the SA necessarily follows.