30.What are experts using to stop birds from flying into the train
A.Tunnels.B.Tracks.C.Protective shields.D.Protective nets
31.What is the passage about
A.Qinling Mountains.
B.How to protect pandas and crested ibises.
C.Xi'an Chengdu high-speed railway.
D.Protective shields and nets.
D
For years,doctors have given blood to patients who need it to survive.These transfusions()
usually include giving red blood cells to patients.
Blood transfusions aren't as simple as taking blood from one person and giving it to someone
else.There're several different blood types that don't all mix well.If someone gets a transfusion of
the wrong kind of blood,their body will reject the blood cells,causing problems.For the first time
ever,scientists from the University of Bristol,Britain,are carrying out a new trail:testing red
blood cells grown in a laboratory on human volunteers.The scientists have used stem cells
from a blood sample to grow billions of brand new red blood cells.
This could be even better than a regular blood transfusion.For one thing,they can be adjusted
for people with different blood types.That'll be extremely helpful for people with rare blood
types.Also,a normal transfusion has red blood cells of all different ages,which means only a
small part of them are brand new.The red blood cells grown in the lab are brand new,and this
means they last longer and that patients will need fewer transfusions.
To test its safety,researchers have given a couple of teaspoons of the blood to two healthy
people,both of whom seem to be doing just fine after the transfusions.In all,they'll be tested on
10 people,and compared to normal transfusions.The new process doesn't indicate that normal
blood transfusions will disappear.Meanwhile,growing red blood cells in a lab is extremely
expensive.And a lot of work and testing still need to be done.But if it's successful,the process
could make life much easier for patients who often need transfusions-even those with rare blood
types.
32.What is special about the red blood cells in the experiment
A.They're given by those with rare blood types.
