A Researcher Noticed That, for Streams Along the East Coast

Multiple Choice

A researcher noticed that, for streams along the East Coast, the amount of money spent on restoration and the number of distinct fish populations present appeared to have a negative correlation.
The researcher concluded that a lurking variable must be present. What does the researcher mean by a "lurking variable"?

A) A variable that is not among the variables studied but that affects the response variable
B) A variable that is the true cause of a response
C) A variable that produces a large residual
D) A variable that is also affected by the explanatory variable