Blood is important to support our lives. But for now, the only way we can get more of it is through donation. And donated blood has its own problems. First of all, certain blood types are extremely rare. Type O negative blood (O-), for example, only    (exist) in 7 percent of people, according to Sunday Times. There are fewer     (donate) and therefore there isn’t enough of this type of blood for everybody who needs it. In addition, donated blood comes from various people, which means that it has to     (examine) carefully for diseases such as HIV to make sure that it’s safe for transfusion(输血).
This is__ scientists all over the world have been trying to make blood in labs. And now, someone finally succeeded—Marc Turner at the Scottish National Blood Transfusion Service has produced blood fit for transfusion, reported Forbes. Different from many ____ scientists, who have tried to make blood by mixing up different ingredients together, Turner chose to grow blood      (direct) from human stem cells. He developed     special technique to create a chemical environment similar to that in our bone marrow (骨髓). This environment encourages stem cells to develop fully      red blood cell.
According to Turner, his artificial blood is     (likely) to contain disease viruses or produce side effects. And the best part is that      he managed to produce was type O- blood. Not only is it a rare blood type, it’s also a universal type, which means it can be transfused into any patient.