Dr. Bramlet has built model hearts for different kinds of heart operations. All of the operations were successful. In his first case, digital images showed only one tiny hole in a baby's heart. But the 3D printed model showed several defects that the baby was born with. Dr. Bramlet says those defects could not be seen easily in the images. The heart surgeon was able to change the type of surgery for the patient based on the 3D model. He adds that 3D heart models saved time during heart operations.

　　Kathy Magliato is a heart surgeon. She welcomes the new technology. She says it could help her make better decisions before she operates on the hearts of her patients.

　　Matthew Bramlet continues to research the technology. He is working with the National Institutes of Health to build a 3D library that includes heart models and images that others can use.

　　【解题导语】　文章主要讲述了研究人员目前正在使用3D打印技术创造的人类心脏模型，来帮助外科医生更好地救治病人。

　　5．What's the limitation of digital heart images?

　　A．A lack of close details.

　　B．Inability to display defects.

　　C．Failure to show personal differences.

　　D．Inaccuracy in the size of the child's heart.

　　C　解析：推理判断题。根据第二段中的"Surgeons regularly use digital images to explore the heart in close detail. But no two human hearts are alike．"可知，外科医生经常使用数字图像来仔细研究心脏。但是没有两个人类的心脏是相像的。故可推知数字图像没有显示出个人差异，故选C项。

　　6．What can the heart model created by 3D printing do?

　　A．It can replace the human heart.

　　B．It can conduct heart operations.

　　C．It can make defects readily apparent.

　　D．It can serve as an alternative to a CAT scan.

　　C　解析：推理判断题。根据第二段最后一句"The 3D printed model adds a new dimension to heart surgery, allowing surgeons to see defects that might not be readily apparent in digital images．"可知，3D打印模型为心脏手术增加了一个新的维度，让外科医生能够看到在数字图像中可能没那么显而易见的缺陷。故可推断出，3D打印心脏模型可以让心脏缺陷显而易见，故选C项。

7．What can we learn from the fourth paragraph?