Answer: Pre-operational stage
Explanation:
The pre-operational stage is one of the type of Piaget's theory and in this stage the children are basically start think at the symbolic development level.
In the pre-operational stage the children basically using the various types of symbols for representing the different the words and it occur at the age of two- seven years.
According to the given question, the Paul is using the pre-operational stage for representing their thoughts. Therefore, Pre-operational stage is the correct answer.