A researcher wants to understand how customers' social interaction with online retailers impact their loyalty to online retailers. This researcher understands that extraneous variables such as gender and age could influence the result, but these variables cannot be eliminated and their effects cannot be canceled out in this case. In order to deal with extraneous variables, which of the following techniques this researcher can choose?

a. Randomization
b. Inclusion
c. Statistical Control
d. Elimination
e. Induction
f. Manipulation