conclusion: 3) chance of being elected - >understand economics
The first and second statements do not link up. It's clear that the argument is attempting to use the contrapositive of the first statement to link up with the second statement, but this does not work because we do not have like terms on opposite sides of the arrow that match, which means we cannot link the statements together.
Based on these statements, the author could conclude that the only people who have a chance of getting elected are those that don't support the tax plan. However, the author can't conclude that they have to understand economics because there could be lots of people who do not understand economics but still do not support the tax plan.
Let's look at the answer choices now.
(B) says, "truly understand economics have no chance of being elected"
The argument concludes that the only people who have a chance of getting elected are the people who understand economics. This leaves open the possibility that some subset of that group has no chance of getting elected for some reason other than supporting the tax plan, which is why we can get rid of (B).
(D) says, "do not support the tax plan do not truly understand economics"
(D) looks great. The argument moves from the idea that people who understand economics do not support the tax plan to the idea that those are the ONLY people who do not support the plan. However, there could be all sorts of other people who don't know anything about economics and still do not support the tax plan. (D) picks up on this, so it's the correct answer choice.
Hope this helps. Let us know if you have any other questions!
