In order to maintain a high standard of living, a nation must maintain a functioning infrastructure.
Conclusion (Hence)
A nation whose standard of living is on the rise can be safely assumed to be a nation that has invested heavily in improving its infrastructure.
Evidence
Maintaining a high standard of living requires maintaining a functioning infrastructure.
Major investment in improving infrastructure will lead to a nation with a corresponding rise in standard of living.
Evaluate
Whenever we're doing Flaw and we see any conditional logic in the premises, we immediately start assuming we'll going to probably see a Necessary vs. Sufficient flaw (where the author supplies a conditional relationship or two in the evidence, but then applies that rule in some backwards or opposite manner to reach the conclusion).
The first sentence has "in order to X, you must Y". The second has "doing A will lead to B".
The conclusion is also a pseudo-conditional, because it's saying .
So we might need to diagram these if we're trying to figure out exactly where the author might be making an illegal reversal or negation.
Prem 1: maintain high S.O.L → maintain functioning Inf
Prem 2: major invest in improving Inf → rise in S.O.L
Do those two premises chain together? No, not really. To chain, you need an overlapping term. "Standard of living" is an overlapping term, but we're talking about it in two different ways -- whether or not you're maintaining a high standard of living / whether or not your standard of living has risen higher than it previously was.
If those were the same we could make this chain: major invest → high S.O.L → maintain in impr Inf. funct. Inf
But they're not. You could raise your standard of living from 150th in the world to 140th. It would be higher but it wouldn't be a high standard of living that you're maintaining.
Okay, so the conditional premises don't chain together. So is there a conditional logic problem with the conclusion? Yes.
The conclusion looks like this: S.O.L is rising → Invested heavily in imp Inf
That's an illegal reversal of the 2nd sentence: invest heavily in imp Inf → rise in S.O.L.
We were told that major investments would lead to a rise in S.O.L.
But other things might also lead to a rise in S.O.L (better daycare and family leave options / cleaner environments / industrial ingenuity creating new jobs and wealth like in Silicon Valley).
If a country's standard of living is on the rise, we can't assume it's because of major infrastructure investment. It might be because of one of these other things that cause standard of living to rise.
Goal
Look for an answer complaining about the illegal backwards conditional move ().
Or look for an answer making the more conversational objection that .