In conducting a simulation using cards to test for the linear association between two quantitative variables, cards that have the values of the response variable are shuffled and then: 

A. Put in two piles of equal numbers. 

B. Put in two piles, though not necessarily equal in number. 

C. Put in the number of piles that correspond with the number of categories in the explanatory variable. 

D. Matched up with values of the explanatory variable.