Which of the following is a key difference between social evolutionism and diffusionism?

Question

a. each are now recognized as fundamentally accurate approaches
b. evolutionism suggested that “primitive society” was better off than its “civilized” counterpart (e.g. the idea of the noble savage)
c. each were concerned with trying to understand “other” (or exotic) cultures
d. diffusionism sought to explore how cultural traits spread from one place to another, evolutionism did not