Final answer:
A capsule is a type of glycocalyx that is firmly attached to a cell, offering protection and aiding in attachment to surfaces. It is not to be confused with other bacterial cell structures like flagella or pili. The answer to the question is a) Capsule.
Step-by-step explanation:
A capsule is a type of glycocalyx that is firmly attached to the cell, as opposed to a slime layer, which is less organized and loosely attached. Most prokaryotes have a peptidoglycan cell wall, and many have a polysaccharide capsule for extra protection, to help maintain cell shape, prevent dehydration, and enable the cell to attach to surfaces in its environment. The correct answer to the student's question is a) Capsule.
Other structures like the flagellum, pilus, and plasmid serve different functions in bacterial cells. Flagella are used for locomotion, pili are involved in the exchange of genetic material during conjugation, and plasmids carry genetic information. However, these are not types of glycocalyx.