Answer the following question given this paragraph: 

Many prokaryotes have an extra layer, called a capsule, outside the cell wall. The capsule protects the cell from chemicals and drying out. It also allows the cell to stick to surfaces and to other cells. Because of this, many prokaryotes can form biofilms, like the one shown in Figure below . A biofilm is a colony of prokaryotes that is stuck to a surface such as a rock or a host’s tissues. The sticky plaque that collects on your teeth between brushings is a biofilm. It consists of millions of bacteria.


Q: A biofilm is a colony of what that is stuck to a surface such as a rock or a host’s tissues?

 Choices:

- insects

- eukaryotes

- vacuoles

- prokaryotes

A:
prokaryotes
