IKMC 2024 - Grades 5-6 - Self-study Question 8

There are eight boxes on a lorry (see picture). A worker cannot pick up a box with another box lying on top. He puts each box on the floor or on another box and touches each box only once. Which tower cannot he build?

Source note: the printed sentence says “eight”, but the diagram and options show the six labelled boxes A–F. Use the illustrated boxes.