Which of the Following Is TRUE of Concomitant Variation

Which of the following is TRUE of concomitant variation?

A) Concomitant variation is a measure of the extent to which two variables vary together.
B) The "pure" case of concomitant variation is found in 20-30 percent of all causal research studies.
C) If perfect concomitant variation is found, we can say that our hypothesis is proven.
D) If there is no evidence of concomitant variation in a two-way cross-classification table, we can be sure that there is no causal relationship.
E) They are all false.