According to Freud, what happens if sexual development is blocked or frustrated at some stage?

René Descartes introduced the notion of the:

a. tabula rasa b. structuralist approach c. reflex arc d. natural selection of behaviors

A scientist who studies how clinical psychotherapy can be used to improve the mental health of depressed patients is conducting

a. applied research. b. correlational research. c. variable research. d. experimental research.