Which of the following is NOT a 'principle of judicial self-restraint' ?
a. the Supreme Court is required to follow all of its past precedents no matter what
b. in order to sue, the plaintiff must have "standing," having suffered (or be about to suffer) some harm or injury
c. federal courts are not to render advisory opinions
d. courts will not hear cases that have become "moot" (i.e. the facts of the case or status of the parties have changed)