According to Douglass, why is the maxim "A still tongue makes a wise head" one that many slaves know and follow?

A.

Slaves know that the songs they sing may annoy the overseers.

B.

Slaves know that they should only ask questions when they are invited to do so.

C.

Slaves know that they should speak to others only in code.

D.

Slaves know that speaking out against their treatment will likely bring punishment.