The less suitable materials for making a face mask among the options provided would be:
O a. Plastic
O b. Glass
O c. Cotton
© d. None of the above
The most unsuitable materials in this context are a. Plastic and b. Glass. These materials do not provide the proper filtration or comfort needed for a face mask. Cotton is a suitable material as it is breathable and can provide a level of filtration. Therefore, if you choose one, you might specifically select b. Glass as the least suitable option for face masks.