Apositive correlation a causal link, and a negative correlation a causal link. a. always indicates, does not necessarily indicate b. does not necessarily indicate, does not necessarily indicate c. does not necessarily indicate, always indicates d. always indicates, always indicates

The answer is B. 
A positive correlation does not necessarily indicate a causal link while a negative correlation does not necessarily indicate a causal link. Correlation might exist but that does not guarantee that one causes the other to change. It does not mean that one factor directly affects the other. Only scientific studies can show the cause and effect of things. But mere correlation is not enough of a cause.