This stimulus provides some conditional reasoning, with the conclusion presented in the first sentence:The economy is doing badly. This is based on the premise that two indicators (real estate and car sales)are performing poorly.
real estate slump
and
bad economy likely
poor car sales
(Note that the author’s logic requires that
both indicators perform poorly in order to draw the conclusion that the economy is probably doing badly).
Answer C provides that Poorly performing real estate or car sales performance is consistent with a good economy. This, however, does not mean that a healthy economy is
likely, only that it is
possible.
Answer D is the correct answer choice, as it reflects the logic from the contrapositive diagrammed above: A healthy economy (“Bad Economy” from the diagram) means that at least one of the two variables (real estate & car sales) is not faltering, which rules out at the possibility that both indicators are performing poorly.
As for your second question, consistency just means lack of inconsistency. If there is no inconsistency between two premises, those two premises are consistent. In LSAT terms, then, "consistent" just means Could Be True; "inconsistent" would mean Cannot Be True.
I hope that's helpful! Let me know--thanks!
~Steve