Cyrus is studying the effects of meditation on coping with illness. In his sample of participants with serious illness, he has the treatment group do an hour-long meditation and the control group listen to the news for an hour. To eliminate the possibility that the meditation, rather than a difference in how comfortable the chairs used by the treatment and control group participants were, causes changes in the participants' coping, Cyrus should use: _______

A. random assignment
B. random sampling
C. experimental control
D. a prospective design

Answer: C. experimental control