What procedure can a researcher use to make sure that the various participant groups are kept roughly equivalent before exposure to an independent variable?

For someone who likes both movies and concerts, choosing between going to one or the other represents an __________ conflict

a) approach-avoidance b) avoidance-avoidance c) approach-approach d) incompatible demands

Freud's ideas provided the foundation for ______

a. existential psychology b. behavioral psychology c. psychodynamic theory d. behaviorism