What "self-conscious" emotion is the most relevant to the moral development ? being scared embarrassment sadness guilt?

Guilt
guilt is the moral motivator number one. It is the feeling or the fear of the feeling one experiences as a result of participating in a morally wrong behavior. A morally wrong behavior is that which is sanctioned by a person set of traditional and religious believes.

The right answer is guilt.

The self-conscious emotions are the emotions of which we are aware, and also, we are aware of how others react to us. These emotions begin to develop during the 2nd year of life and have social benefits such as moral development, and socially acceptable behavior. For example, the guilt we feel when we conduct a behavior that we consider unacceptable prevents us from performing the behavior again.

I hope this information can help you.