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Module6 Animals in Danger Ⅰ.阅读理解 阅读下列短文，从每题所给的四个选项(A、B、C、D)中，选出最佳选项。 A Long nights of winter can leave even the most positive people feeling cranky (古怪的)．But for about 5% of Americans，it's more serious: seasonal affective disorder (SAD) is a type of depression that most occurs in the winter. Symptoms include loss of energy，eating more and difficulty in concentrating. The cause of SAD is unknown，but darker days probably play a role. Reduced levels of natural sunlight can disrupt your body's internal clock，which can lead to depression.It also causes a drop in serotonin (血清素)，a feel－good brain chemical. Severe cases may need antidepressant treatment.You can't prevent the disorder from developing，but you can ease the symptoms. Consider light therapy Exposure to bright light that mimics (模仿) natural light is thought to affect mood－related brain chemicals and ease symptoms. It involves sitting in front of a special light box or wearing a cap－like lighted visor(盔甲)，for about 30 minutes a day.Another therapy uses a “dawn simulator” that is turned on early in the morning and gradually increases in brightness，allowing your body to wake up naturally. Light therapy can have minor side effects，such as eye strain and headaches，and it isn't recommended for people with skin sensitivity. | 
