I think I should give the reason for my being in Birmingham, since you have been influenced by the argument of “outsiders coming in.” . . . Several months ago our local affiliate here in Birmingham invited us to be on call to engage in a nonviolent direct action program if such were deemed necessary. We readily consented and when the hour came we lived up to our promises. So I am here, along with several members of my staff, because we were invited here. I am here because I have basic organizational ties here. –“Letter from Birmingham Jail,”
Martin Luther King Jr.

What does King mean by the phrase "a nonviolent direct action program”?

a peaceful form of protest, such as a sit-in or march
white Southern resistance to a civil rights protest
a legal case to bring about change via the courtroom
a negotiation between civil rights protestors and local politicians