The correct answer is: Paul's immune system functioning will improve.
Prolonged stress suppresses and negatively affects the functioning of a person or animal's immune system. Due to this, a person is more susceptible to infectious diseases such as colds, gastroenteritis, etc. Stress suppresses immune system functioning due to increased levels of cortisol, which in turn lowers the number of lymphocytes (antibodies that fight illness and infection. If Paul's lifestyle changes from a highly stressful one (as a stockbroker), to a more relaxing one (running a yoga studio in the tropics), his immune system functioning will improve.
Answer: Gambler's fallacy
Explanation: Gambler's fallacy is most often believed by gamblers. It is the assumption that a departure from what normally occurs on average, or in the long run, will in the short run be correct. In other words, that a past random event influences the outcome of a future random event. It is also referred to as the Monte Carlo fallacy.