Which of the following is a characteristic of concrete operational thinking?
a. the ability to have complex abstract thought
b. the ability to understand conservation of matter
c. the ability to sort items by one characteristic only
d. the ability to formulate hypotheses or guesses

The correct answer is B. the most important developments in this stage is an understanding of reversibility, or awareness that actions can be reversed. An example of this is being able to reverse the order of relationships between mental categories. So, they can understand conservation of matter.

Hydrophobia (fear of or aversion to water).