You Want to Study the Effects of Training on Performance

Multiple Choice

You want to study the effects of training on performance.Because you must get permission to train people,you ask for volunteers.You train the volunteers,and then measure the performance of both volunteers (trained) and non-volunteers (non-trained) .You have used

A) both random assignment and random selection.
B) random assignment but not random selection.
C) random selection but not random assignment.
D) neither random assignment nor random selection.