Scientists now know that people are born with a general tendency toward a certain level of happiness, and that they tend to maintain that mood in their day-to-day lives.

       About half of a person’s “happiness quotient (份额)” comes from the personality he or she is born with. So, what about the other half of the happiness quotient? About 10 percent of that quotient depends on outside circumstances, such as how much money people make or how healthy they are. The remaining 40 percent, says psychologist and happiness researcher Sonja Lyubomirsky of the University of California, is entirely up to themselves.

       In one recent study, she and her colleagues assigned more than 300 college students to complete one of three activities. For 15 minutes a week over 8 weeks, the first group of these students wrote about what their lives would be like in the future if all their hopes and dreams came true. The second group spent the same amount of time writing letters to people who had done things in the past that the letter writers were grateful for. The third group of students simply listed everything they had done in the past seven days.

       The purpose of this experiment was to find out whether expressing optimism about the future or gratitude for the past could make a person happier.

       Results backed previous research, which had shown that expressing optimism and gratitude led to an improved sense of well-being.

       In other words, only people who really wanted to be happier were able to make that happen.

1．According to the passage, how many factors are there in deciding people’s happiness?

     A．Three.                 B．One.                   C．Four.                  D．Five.

2．Which group of the students needs imagination in the experiment?

       A．The second group.                               B．The third group.  

       C．The first and third groups.                    D．The first group.

3．According to the text, if you want to be happier, you should _____________.

     A．laugh when you were born

     B．try to make more money and improve your health condition

       C．imagine what your life would be like in the future and write to people who have done things for you every day.

     D．be optimistic about the future and grateful for the past

4．The writer of the passage intends to tell us that _____________.

       A．happiness is mostly decided by your birth

       B．optimism and gratitude equal happiness

       C．happiness can be decided by yourself  

       D．happiness decides your success