Jeff can think in images and symbols, has acquired basic language skills, and has an "intuitive" intelligence. He has yet to appreciate that certain aspects of objects remain unchanged despite changes in their appearance. Piaget would contend that Jeff is at the stage of development.

The correct answer to the following question will be "Preoperational".

Explanation:

The preoperative or preoperational stage seems to be the second phase of cognitive development philosophy by Piaget.This phase starts about the age of two and will last until about 7 years old. Infants are considered on some kind of abstract level throughout this time but were not using conceptual actions yet.

So that, in the given scenario Piaget will also argue that Jeff would be in the developmental preoperative stage.