题目内容：
阅读下文，回答题。Facts about Stroke
1 Every 45 seconds,someone in America has a stroke.Every 3.1 minutes,someone dies of one.Stroke killed an estimated 167,661 people in 2000 and is the nation's third leading cause of death,ranking behind diseases of the heart and all forms of cancer.Stroke is a leading cause of serious,long-term disability in the United States.
2 Stroke is a type of cardiovascular(心血管的)disease.It affects the arteries(动脉)leading to and within the brain.A stroke occurs when a blood vessel that carries oxygen and nutrients(营养物)to the brain is either blocked by a clot(凝块)or bursts.When that happens,part of the brain cannot get the blood(and oxygen)it needs,so it starts to die.
3 The brain is an extremely complex organ that controls various body functions.If a stroke occurs and blood flow can't reach the region that controls a particular body function,that part of the body won't work as it should.If the stroke occurs toward the back of the brain,for instance,it's likely that some disability involving vision will result.The effects of a stroke depend primarily on the location of the obstruction(阻塞)and the extent of brain tissue affected.
4 The American Stroke Association has identified several factors that increase the risk of stroke.The more risk factors a person has,the greater the chance that he or she will have a stroke.Some of these you can't control,such as increasing age,family health history,race,and prior stroke.But you can change or treat other risk factors to lower your risk.Factors resulting from lifestyle or environment can be modified with a healthcare provider's help.Some of these include:high blood pressure,current smoking,heart disease,and high red blood cell count.
5 A stroke can happen to anyone at any moment.In fact about 600,000 people have strokes every year.For many years,there was no hope for those suffering a stroke.However,recent breakthroughs have led to new treatments.For the treatments to work,the person must get to a hospital immediately.
Paragraph 2__________. A．Effects of a stroke
B．Annual cost of stroke in the US
C．Definition and description of a stroke
D．Breakthroughs in treatment
E．Risk factors of stroke
F．Warning signs of a stroke
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