Why do radical behaviorists say that mental constructs like "thought process" and "ideas" are useful? Pick the three most correct statements:

a. Things do not have to exist to cause us to behave the way we do.

b. Ancient philosophers came up with qualities they believed MUST exist in everything.

c. Differences in opinion are because of lack of training and cannot be "the stuff of science"

d. When psychology broke away from philosophy they took a structuralist approach to create a periodic table of human behavior (using introspection).