In a Laboratory,smokers Are Asked to "Drive" Using a Computerized

In a laboratory,smokers are asked to "drive" using a computerized driving simulator equipped with a stick shift and a gas pedal.The object is to maximize the distance covered by driving as fast as possible on a winding road while avoiding rear-end collisions.Some of the participants smoke a real cigarette immediately before climbing into the driver's seat.Others smoke a fake cigarette without nicotine.You are interested in comparing how many collisions the two groups have.In this study,the cigarette without nicotine group is the:

A) control group.
B) correlation group.
C) experimental group.
D) placebo group.