Adults Are Capable of Abstract Thought

Adults are capable of abstract thought. In contrast, children are concrete thinkers, meaning they are able to think about things in "here and now." Which is an example of a concrete way of thinking?

A) Touching a couch or table and identifying it as a piece of furniture
B) Understanding a couch or table as part of the general class of furniture
C) Understanding a couch or table as separate useful items, and as representatives of a general class (furniture)
D) Understanding a couch or table as separate useful items, rather than representatives of a general class (furniture)