I agree with you that D is correct. I also think that "that there is little of significant difference" would be correct but "differences" is perhaps what makes E incorrect.
The investigations of many psychologist and anthropologists support the generalization of there being little that is a significant difference in underlying mental processes manifested by people from different culture.
Between D and E ....
A and B are strick off becoz of being ..C is akward ..
A of there being little that is a significant difference
B of there being little that is significantly different
C of little that is significantly different
D that there is little that is significantly different - as explained in E
E that there is little of significant differences ...standalone this underline part is gramatically ok ...but do no gel with the entire sentence ...sentence ask for ....X is different from Y ,w which is reflect in option D .