Read the excerpt from Narrative of the Life of Frederick Douglass.

I had resided but a short time in Baltimore before I observed a marked difference, in the treatment of slaves, from that which I had witnessed in the country. A city slave is almost a freeman, compared with a slave on the plantation. He is much better fed and clothed, and enjoys privileges altogether unknown to the slave on the plantation. There is a vestige of decency, a sense of shame, that does much to curb and check those outbreaks of atrocious cruelty so commonly enacted upon the plantation.

In this paragraph, what connotation does “shame” have?

feeling proud
knowing right and wrong
having regret
feeling humiliation