A researcher reports an inverse relationship between weight and exercise level for a group of 8-year-old children (greater weight is associated with less exercise). However, the researcher suspects...

A researcher reports an inverse relationship between weight and exercise level for a group of 8-year-old children (greater weight is associated with less exercise). However, the researcher suspects that the children’s rate of metabolism may be responsible for the relationship. That is, children with higher metabolism exercise more and weigh less than children with lower metabolism. This is an example of

 a. the third-variable problem.

b. the directionality problem.

c. the reversal problem.

d. the criterion problem.