An Automobile Dealer in Houston,after a Very Cold Winter,found Himself

An automobile dealer in Houston,after a very cold winter,found himself with a very large inventory.He experimented with offering a free trip to New York (independent variable) with every car sold.He recorded sales (dependent variable) after the promotion.This is an example of

A) exploratory.
B) causal.
C) descriptive.
D) continuous panel.
E) All of the above.