Refer to the Figure, Which Shows the Formation of a Biofilm

Refer to the figure, which shows the formation of a biofilm. According to the figure, which statement about biofilms is true?

A) Only one species of microorganism can inhabit any one biofilm.
B) A biofilm matures once it attaches to a substrate.
C) Signaling molecules from the biofilm attract other organisms.
D) Signaling molecules from the biofilm digest the matrix.
E) Species that normally occur in biofilms cannot be free-living.