题目内容：

    Heart disease is one of the major killers in the world today. Many who suffer from it must have heart transplants (移植). However, it’s difficult to get a suitable heart donation, and even if a patient survives the wait, his or her body often rejects (排斥) the heart.

But there is now new hope for sufferers of heart disease. According to a study published in the journal Advanced Science, researchers from Israel’s Tel Aviv University printed a 3D human heart on April 15.

“This is the first time anyone anywhere has successfully engineered and printed an entire heart,” professor Tal Dvir told CNN.

Unlike the previous 3D-printed heart structure, the new heart is complete with cells, blood vessels (血管), chambers (心室) and other structures a heart needs to function normally. But scientists still have more to figure out before the 3D-printed heart can be fitted into the body. For one thing, the experimental heart is only the size of a thumb (拇指). And, although it can contract (收缩) like a muscle, it cannot pump out blood like a real one. At present, the heart prototype (样品) is like a tiny airplane that has all of the right parts, but can’t fly.

However, the development is still regarded as a major breakthrough in medicine.

In the experiment, the researchers turned human fat tissue (脂肪组织) into human heart tissue with stem cell (干细胞) technology. The tissue was then turned into “bio-ink” for a 3D printer to ensure that tissue in the heart came from the patients themselves. So ideally, if it were to be placed in the body of someone in need of a transplant, there would be less risk of organ rejection.

“Patients will no longer have to wait for transplants or take medications to prevent their rejection,” researchers told USA Today. “Instead, the needed heart will be printed, fully personalized (个性化的) for every patient.”

But the scientists think that 3D printing can be used to create other human organs. They foresee a time when the 3D printing of organs will be an everyday medical practice.

“Maybe, in 10 years, there will be organ printers in the finest hospitals around the world and these procedures will be conducted routinely,” Dvir said.

1.Why is the 3D-printed heart important?

A.It will be used on a patient.

B.It is the first 3D-printed heart.

C.It will replace a heart donation.

D.It has a complete heart structure.

2.What problem do 3D-printed hearts have?

A.They cost too much. B.They are too small.

C.They can’t contract. D.They are hard to produce.

3.Why would there be less risk of organ rejection with the 3D-printed heart?

A.It would be made with stem cell technology.

B.It would be made from human fat tissue.

C.It would come from a patient’s body.

D.It would be printed according to the patient’s condition.

4.What attitude does Tal Dvir hold toward the future of 3D printing of organs?

A.Confident. B.Doubtful.

C.Worried. D.Confused.