单选题 Imagine that you have woken up on the first day of your vacation.You enjoy a delicious breakfast,take a walk on the beach and read the morning newspaper. You are feeling happy and relaxed. But you may start to feel bored by the time the late afternoon comes around!If you have ever felt like this,you're not alone.It turns out that having unlimited(无限的)free time is not always as great as we expected. What is the best amount of free time for our happiness?Researchers tried to answer this question by surveying tens of thousands of people, collecting data(数据) on how they spent their time and how happy they were. After looking at the data,the research team found that having less than two hours of free time a day is not enough to be happy. People who have less than two hours of free time a day usually have more stress.It means that they are simply too busy with work to get their happiness.The fact that being too busy cuts happiness might lead to the answer that more free time is simply better. Surprisingly,having a lot of free time is not a panacea for happiness, according to the research. People surely get a certain sense of joy from finishing tasks. So having more than five hours of free time a day sometimes makes us lose the sense of achievement and joy.I think it is how we spend our free time that matters. When free time is used in more active ways,like playing a team sport, then five or more hours a day can keep or even increase happiness. However,spending five or more hours of free time doing nothing can stop happiness小题:hich does the writer think is important for happiness