Answer:
a) subgoaling.
Explanation:
You have to cook dinner for 30 people on saturday, this is the big goal. However, you start doing different little projects since thursday that will help you reach your goal of preparing the dinner party (getting groceries, cleaning the apartment, do laundry, etc). Since you are "breaking" the goal into smaller actions to be achieved, this is an example of subgoaling.
*It is not using algorithms since an algorithm is the use of an strategy that guarantees to solve the problem.
*Using heuristics would be using a practical method that does not necessarily guarantees to reach the goal.
*Finally, prototype would be to try different approaches to see which one turns out best to finally use that one in order to achieve a goal.