In the Absence of Any Additional Information,which of the Following

In the absence of any additional information,which of the following conclusions may be drawn with certainty from a positive correlation between intelligence test scores and brain volume?

A) A larger brain produces higher intelligence.
B) Higher intelligence results in a bigger brain.
C) Factors like better nutrition yield both a larger brain and higher intelligence test scores.
D) Intelligence test scores and brain volume are related but exactly what that means is unclear.