A Medical Doctor Believes That the Administration of Aromatherapy Will

A medical doctor believes that the administration of aromatherapy will reduce the anxiety of first-time mothers-to-be during labor and will increase their reported satisfaction with their care at his hospital.He randomly assigns mothers to give birth in a room either with or without aromatherapy.What is the independent variable in this example?

A) Anxiety level during labor
B) Number of previous birthing experiences
C) Room environment
D) Satisfaction with hospital care