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 the artificial blood can be  manufactured on a large scale. "It is one thing to bake a cake and another  thing to bake a cake 100 times the size," said Turner. "It's not just a matter  of putting in 100 times the ingredients." Which of the following  words best describes Turner's attitude towards theapplication of his  artificial blood?
Pessimistic. Doubtful. Cautious. Uninterested.
Question: 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 the artificial blood can be  manufactured on a large scale. "It is one thing to bake a cake and another  thing to bake a cake 100 times the size," said Turner. "It's not just a matter  of putting in 100 times the ingredients." Which of the following  words best describes Turner's attitude towards theapplication of his  artificial blood?
A. Pessimistic.
B. Doubtful.
C. Cautious.
D. Uninterested.
Answer: