阅读下面的短文，在空白处填入一个适当的词，或填入括号中所给词的适当形式。

    People are always giving out advice on how to be happier. And many studies have different(opinion) on what it means to be happy.

    Joseph Mercola, a US physician, found that(health) habits could lead to a happier lifestyle. He found(happy) people eat right, exercise and get better sleep.

    But Sir Richard Peto, a teacher in Oxford University, didn't(think) so. His new study found happiness hasto do with your health or how long you will live.

    So far, researchers(study) 1 million UK women for over 10 years. The womenquestions on their health, happiness, amount of stress and how they felt about their.

    They found unhappy people were no more likely to get sickhappy ones.

    So what do you think it(mean) to be happy?