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 cannot be...

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 cannot be sure whether the extra weight is preventing the children from exercising or whether the lack of exercise is leading to greater weight. This is an example of

a. the third-variable problem.

 b. the directionality problem.

 c. the reversal problem.

d. the criterion problem.