Bob has a beaker filled with an unknown liquid and must determine what it is. he decides to systematically use a number of tests to determine the correct answer. according to piaget, bob has most likely reached the stage of cognitive development.
(a) sensorimotor
(b) preoperational
(c) concrete operational
(d) formal operational

Correct answer is "D"

Explanation:

There are four stages of cognitive development. The last stage is the formal operational stage, it can be demonstrated when the person is around 12  years and continues until adult.

During this period, the person shows the potentially of criticism, making the use of reason and argument.

This is also characterized by the capacity to demonstrate the ability of thinking, create conclusions supported by

structured suppositions.

answer; product market;