Hi, this looks like there's some sort of error here! I can try to take a stab at why a-d are wrong.
The overall argument is structured to prove that an end to a recession is coming. The evidence cited for that is that people are buying durable goods, and this indicates that people expect growth. We are asked what role the fact that people are buying durable goods plays. We know that it is a piece of evidence or a premise in the argument that the recession will end.
A is wrong because the author isn't trying to explain why people are buying more, but is using that fact to explain why the recession will end.
B describes a necessary assumption, which is not at all what the statement was.
C is wrong because it is not inferred, it is just stated.
