As shown in the figure, this is the floor plan of a luxury suite in a hotel. In order to save costs, the customer adopted a deployment solution in which a single AP covers two rooms. If this…

As shown in the figure, this is the floor plan of a luxury suite in a hotel. In order to save costs, the customer adopted a deployment solution in which a single AP covers two rooms. If this deployment solution is adopted, in order to ensure the coverage effect, which of the following materials are not recommended for the middle wall? (Multiple choice)