Hi Barath!
I'd be happy to help sort through the answer choices on this one.
To begin, we're given conditional reasoning in the first sentence, "anyone who supports the new tax plan [STP] has no chance of being elected [E]," which can be rewritten as:
STP 
E
Its contrapositive is:
E STP
That generic form (A
B) can also be rewritten as a double-not arrow:
E 
STP
We're also told, "anyone who truly understands economics (TUE) would not support the tax plan (STP)," or:
TUE STP
As earlier, this is the same as:
TUE STP
Or:
STP TUE
It's possible to connect these:
E STP TUE
In other words, this is saying that if one is elected, then one did not support the plan, and if one supported the plan, then one does not truly understand economics.
The author then reaches a conclusion, "only someone who truly understands economics would have any chance of being elected." This is where the flaw comes into play. We're told in the above conditional reasoning that someone supporting the new tax plan doesn't have a chance of getting elected--support for the new tax plan is sufficient to be not elected, and it's necessary not to support it to be elected. We also know that economists
won't support that new tax plan, but we don't have more from the stimulus on this front. That is, we know what happens if someone supports the new tax plan (the person becomes un-electable), and also we know that if a person is elected, the person did not support the plan.
But the conclusion is ultimately too limited. There could be others besides only "someone who truly understands economics" who might also not support the tax plan. Just because understanding economics is sufficient to establish that a person won't support that new tax plan, this doesn't prevent others who are non-economists from not supporting it as well. This is what answer choice (D) conveys: it ignores the possibility that some people who "do not support the tax plan do not truly understand economics."
With that in place, it's easier to address (B), (C), and (E). Answer choice (B) states that it ignores the possibility that some people who "truly understand economics have no chance of being elected." The stimulus is making a specific argument that imposes limits: "
only someone who truly understands economics would have any chance of being elected." The stimulus is concluding that the only route to being elected is by truly understanding economics (understanding economics is necessary). That doesn't mean understanding economics is sufficient--even knowing economics, a person might have an unlikable personality, for example. So the conclusion in the stimulus isn't saying that knowing economics guarantees being elected--some may know economics and still have no chance. This is why answer choice (B) doesn't correctly describe a flaw.
Similar reasoning applies to answer choice (C), which states that the argument ignores the possibility that some people who "do not support the tax plan have no chance of being elected." As the diagrams above reflect, not supporting the tax plan is necessary to be elected (E
STP ). Not supporting the tax plan is necessary to being elected, but it's not sufficient on its own to guarantee election; again such a person might be unelectable because of an unlikable personality. So answer choice (C) also isn't a flaw made in the stimulus.
Finally, answer choice (E) states that the argument ignores the possibility that some people who "have no chance of being elected do not truly understand economics." This seems less related to the conclusion. The conclusion in the stimulus is about who has a chance of
being elected. Thus, failing to consider aspects of those who have no chance of being elected seems unrelated to that conclusion. If such material isn't mentioned, that omission doesn't amount to being a flaw.
/TUE
