An unjust law is a code that a majority inflicts on a minority that is not binding on itself. This is difference made legal. On the other hand, a just law is a code that a majority compels a minority to follow, and that it is willing to follow itself. This is sameness made legal." -Dr. Martin Luther King, Jr., Letter from a Birmingham Jail, 1963.

Which of the following constitutional provisions guarantees that "sameness [is] made legal" in King's argument?

a. The establishment clause of the First Amendment
b. The equal protection clause of the Fourteenth Amendment