66. It can be inferred from the passage that the animal model was mainly intended to ____.

1. investigate the possibility of growing blood vessels in the lab
2. explore the unknown functions of the human liver
3. reduce the incidence of liver disease in the U.S.
4. address the source of liver transplants

67. What does the author mean when he says that the livers aren't grown from scratch?

1. The making of a biological scaffold of proteins and extracellular architecture.
2. A huge step toward building functioning livers in the lab.
3. The building of the infrastructure of a donor liver.
4. Growing liver cells in the donor organ.

68. The biological scaffold was not put into the culture in the lab until ____.

1. duplicated synthetically
2. isolated from the healthy liver
3. repopulated with the healthy cells
4. the addition of some man-made blood vessels

69. What seems to be the problem in the planted liver?

1. The rats are wrong recipients.
2. The time point of the transplantation.
3. The short period of the recellularization.
4. The insufficient repopulation of the blood vessels.

70. The research team holds high hopes of ____.

1. creating lab-generated livers for patients within two years
2. the timetable for generating human livers in the lab
3. stem-cell research as the future of medicine
4. building a fully functioning liver into rats

(Reference keys.)