Official Solution By VeritasPrep:
This problem is a great candidate for the Assumption Negation Technique. If you negate the correct answer, D, it becomes:
It is possible for a government to spend money on social programs and also stimulate the economy.
And you can see that this completely invalidates the argument. The given argument claims that the current official lied about saying she would stimulate the economy, with its only premise for that claim being "she has spent a lot of money on social programs." If it is, indeed, possible to spend money on social programs and also stimulate the economy, then that sole piece of evidence doesn't have any value; as it currently stands, spending money on social programs is not at all connected to the stimulation of the economy.
With the incorrect answer choices, note the specificity of the argument, which is "she said she would stimulate the economy, but she lied." Choice A supports a different argument (she's using money unwisely) but doesn't connect to "she is not stimulating the economy." Similarly, choice E adds more value to the premise ("she's spending a lot of money on social programs") but as discussed above that premise is not connected to the conclusion. Choice B goes contrary to his argument - if her spending were the only way to stimulate the economy, as B says, that would directly weaken his argument.
Choice C can perhaps be best understood by negation, too; if you negate C it then says "politicians do not have the ability to stimulate the economy." Note that here this does not weaken the conclusion (as a correct assumption answer will do once negated). Since the politician wants to essentially say that his opponent is not stimulating the economy, if anything this negated answer would help him, meaning that the assumption as it stands does not help him. Therefore, C is also incorrect.