我们今天能见到的长城大多都是在哪个朝代修建的                        （   ）

A．秦朝

B．唐朝

C．明朝

D．清朝

阅读理解

     Part of David's heart muscle grew thick and stiff ,keeping the flow of blood. The disease David had

lived with for 17 years was slowly keeping his heart from beating.

     The night Flora bent forward in front of her computer, everybody else was asleep. For the price, or

keeping her husband a live. To do that, she needed to search for the information:  a place and someone to

fix David's damaged heart. And she needed to be lucky.

     Finally, she found what she needed on a magazine's website. When David came into the study early

the following morning, she said "I've found it" and handed him the papers.

     David wondered if there was any other way. Then he thought about his wife and kids. He stared at

the papers. Only he could make the choice: Should he have the same surgery(外科手术) that had killed

his father,Or the one that no one works? This experiment treatment might be his best hope.

     The operation theatre was kept freezing cold. David wasn't frightened, just nervous.

He felt a burning pain, a burning knife cutting through his heart.

     On the EKG screen, the tiny valley in the middle of each peak(高峰)-showing a sign of David's disease-smoothed out. For the first time in years, he had a normal arterial(动脉) pressure.

     "That's the most unusual thing, "said Flora, excited by the results.

     Three days later, David and Flora drove home after the fight from Houston. Their kids ran out to meet

them.