The correct answer is B. your teacher.
The best person from the list to speak to if you have to make a difficult decision would be your teacher. They should be a responsible, reliable, objective source of advice. Choose a teacher that you have a good relationship with though!
People from your local store will give you personal, biased advice based on what they think they know about you and about their own lives, a stranger knows nothing about your or your situation, a friendly chat room might be of some use but then again most advice from people online might not necessarily be true and reliable.