Researchers studied how increased stress affects the human immune
system. Which of these is a control
variable?
A. Neither increased stress nor the immune system response
B. Both increased stress and the immune system response
OC. Increased stress
OD. The immune system response
system. Which of these is a control
variable?
A. Neither increased stress nor the immune system response
B. Both increased stress and the immune system response
OC. Increased stress
OD. The immune system response