题目

任务型阅读Ebola is a dangerous virus that can cause people to get very sick and even die. The virus is causing the biggest problems in western Africa, where it has spread quickly.   But it can get worse and cause life-threatening symptoms (症状), such as bleeding and trouble breathing.   Ebola does not spread like colds or the flu because it does not float through the air. Ebola also doesn't spread through food or water, like some other viruses. Instead, Ebola spreads when someone touches the body fluids(液体) of a sick person.   An outbrea已知四边形ABCD是平行四边形，则下列结论中正确的是（　　）A. 当AB⊥BD时，它是菱形 B. 当AC=BD时，它是正方形C. 当∠ABC=90°时，它是矩形 D. 当AB=BC时，它是矩形