Answer: The correct answer is "Observational Learning has been found to play a greater role in the development of phobias than direct conditioning.
Explanation: Although some phobias can be learned via Observational learning (seeing others show signs of fears in certain situations) they usually are aquired through direct conditioning.
The most common mechanism over people adquire phobias is classical conditioning and are maintained through operant conditioning which happens when a person associates a certain object with an intense feeling of fear and anxiety.