Please answer the following question: Read the article and select the best answer. Article: Everybody needs blood Have you ever seen buses on the street for donating blood? Medical workers on board collect blood from volunteers. The blood is then stored up and given to people who have lost a large amount of it due to accidents or diseases. Blood is one of the most important substances supporting 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 exists in 7 percent of people, according to Sunday Times. There are fewer donors 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 be examined carefully for disease such as hepatitis and HIV to make sure that it's safe for transfusion. This is why scientists all over the world have been trying to make blood in labs. And now, someone finally succeeded--Marc Turner at the Scottish National BloodTransfusion Service has produced blood fit for transfusion, reported Forbes. Unlike many other scientists, who have tried to make blood substitutes by mixing up different ingredients together, Turner chose to grow blood directly from human stem cells . He developed a special technique to create a chemical environment similar to that in our bone marrow . This environment encourages stem cells to develop fully into red blood cell. According to Turner, his version of artificial blood is unlikely to contain disease viruses or produce side effects. And the best part is that what 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. The new blood is scheduled for human tests in 2016. However, Turner stressed that the new study should not be taken as a signal for people to stop donating blood because it could be another 20 years before... Question: According to the text, a potential danger of blood transfusion is that _ . Options: A: it is impossible to store up large amounts of blood B: blood transfusion may lead to some terrible infections C: it is very hard to find matches for certain blood types D: blood transfusion often leads to serious side effects
A:
B