I'm not an instructor but I can try explaining it. This is a Strengthen with Sufficient Premise question and the conclusion is "countries that put collective goals before individuals' goals cannot emerge quickly from an economic recession". Noting that the phrase "countries that put collective goals before individuals' goal" is something totally out of the blue in the conclusion, right off the bat we can eliminate A and D because we need an answer to connect with this phrase from out of the blue.
D is correct because of the premise "people's confidence in the economic policies of their country is a precondition for any new investment", and if "People in countries that put collective goals before individuals' goals lack confidence in the economic policies of their countries" as D states, then it helps us determine the conclusion that countries that put collective goals before individuals' goals cannot emerge quickly from an economic recession
