In My Bondage and My Freedom, Frederick Douglass expresses his gratitude to those who help him learn to read, but does not identify them because they might get into trouble. Why does he include this information?

to show that Douglass puts the needs of others above his own
to show that the Aulds are unique in their opposition to reading
to show that Douglass is afraid of white people
to show that keeping slaves from reading is a cultural norm