What Is the Significance of the Supreme Court Case, Ford

What is the significance of the Supreme Court case, Ford v. Wainwrigh t (1986) ?

A) It removed the right of the defendant to refuse the insanity defense when the court deemed it appropriate.
B) It required that the police demonstrate, beyond a reasonable doubt, that a suspect fully understood his or her Miranda rights before confessing.
C) Citing the Eighth Amendment, it prohibited the execution of mentally incompetent defendants.
D) It provided defendants with the constitutional right to waive counsel and represent themselves at trial.