Can a Researcher Study the Impact of Two Simultaneous Interventions

Multiple Choice

Can a researcher study the impact of two simultaneous interventions within one study?

A) No, they would need to study the impact of three or more simultaneous interventions.
B) No, this would make it impossible to know which one caused the change.
C) Yes, this increases the odds that the desired result would occur.
D) Yes, this would allow subjects to choose which intervention they wanted to receive.