Researchers have found relatively stable individual differences in each of the following except one. Which one?

The category "animal" has a graded structure, which means that

a. most of the examples are well known to the general public. b. the members of that category are not all equally representative of that category. c. procedural knowledge is more important than declarative knowledge. d. there is a family resemblance among the members of this category.

The exemplar approach to concepts suggests that our categories are based on

a. the most typical items. b. less typical items, as well as highly typical items. c. family resemblance. d. the pattern of connections between the members of a category.