题目

根据短文内容，从短文后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。When the winter comes,millions of Americans realize they don't feel as happy as usual, and may bedepressed If you're one of them, you may be suffering from seasonalaffective disorder or SAD, whose symptoms include exhaustion, difficultyconcentrating, sleep problems, body aches and pains, and a loss of interest inactivities you normally enjoy. Take extra Vitamin D .Researchers at theUniversity of Georgia analyzed more than 100 articles that examined the linkbetween Vitamin 今年春季西南五省发生世纪大旱，为掌握旱灾对粮食生产造成的损失，应采用的方法是（　　）A．模拟实验B．调查法C．实验法D．观察法