Scientists are trying to find out how things affect our feelings. How you feel is controlled by many things, such as your personality , the actions  of others. Maybe you don't know the weather can affect your feelings as well. People often say they feel good when the sun is shining and sad when it is cloudy. In fact, sunlight makes us feel good. When sunlight hits our skins, our bodies makes vitamin D(D). Vitamin D helps our bodies make a special chemical . This special chemical affects our brains and makes us feel happy. For example, there are long, dark winters of little sunlight in Sweden and Norway, so many people in these countries often feel sad. To help the people in these countries feel better, scientists build special "sunrooms" for people to go there and get "sunlight" for an hour or two! The weather can also affect people's feelings in other ways. Hot weather can make people angry because people don't feel comfortable when they are hot. In the same way, rain can make people angry because being wet can be unhappy. As you can see, the weather can have an effect on the chemicals which control our _ . Through these ways, the weather can affect our feelings in these ways. Sadly, while the weather can change us, we cannot change the weather. Which of the following is TRUE about vitamin D according to the passage?
It is a kind of special food. It makes us worried by affecting our brains. It is helpful to our bodies. It is in the sunlight.