Questions 4 to 6 are based on the following passage. At the end of the passage，you will be given 15 Seconds to answer the questions.
Now, listen to the passage.
4. According to the research，the brain is very efficient at
A. pointing out health risks
B. processing good news
C. suggesting a tendency
D. bringing health benefits
5. What is the health benefit of being naturally optimistic?
A. It helps to reduce anxiety.
B. It eliminates the fundamental bias.
C. It lowers the risks of deaths and injuries.
D. It minimizes the likelihood to lose sleep.
6. According to the passage, which of the following is CORRECT?
A. About 80% of people consider themselves to be optimists.
B. Optimists have lower risk of death from heart disease.
C. An upbeat attitude bears no disadvantages.
D. There's no fundamental bias in the brain of an optimist.