Some are more effective than others.
a. decision making methods
c. prophecies
b. heuristics
d. standards

There are two possible answers here, either b - heuristics, or a - decision making methods. Some decision making methods are, as stated in the question, more effective than others are. Which are most effective often depends on the problem, the person who is making the decision, any many other factors. Similarly, having and using heuristics also depends strongly on the situation. Some situations are more suitable for certain heuristics and other situations for other heuristics.