In an Experiment,researchers Exposed Half of the Participants to Loud

Multiple Choice

In an experiment,researchers exposed half of the participants to loud noise during a memory-encoding task.The room was quiet for the other half of the participants.Later,all participants were given a memory test and the number of correct items recalled was obtained for each participant.What is the independent variable?

A) the number of items recalled
B) the noise level during the encoding task
C) the time interval between encoding and recall.
D) the probability of being assigned to the two groups