4．
| A．procedure B．transplant C．attempt D．native E．extinct F．prohibited G．worth H．appreciate I．reintroduce J．undertaken K．groundbreaking |
With only about 1，000pandas left in the world，China is desperately trying to clone the animal and save the endangered species．That's a move similar to what a Texas A&M University researchers have （41）
for the past five years in a project called"Noah's Ark．"
Noah's Ark is aimed at collecting eggs，embryos （胚胎），semen and DNA of endangered animals and storing them in liquid nitrogen．If certain species should become （42）
，Dr．Duane Kraemer，a professor in Texas A&M's College of Veterinary Medicine，says there would be enough of the basic building blocks to （43）
the species in the future．
It is estimated that as many as 2，000species of mammals，birds，reptiles will face extinction in over 100years．The panda，（44）
only to China，is in danger of extinction in the next 25years．
This week，Chinese scientists said they grew an embryo by introducing cells from a dead female panda into the egg cells of a Japanese white rabbit．They are now trying to （45）
the embryo into a host animal．
The entire （46）
could take from three to five years to complete．
"The nuclear transfer of one species to another is not easy，and the lack of available panda eggs could be a major problem，"Kraemer believes．"They will probably have to do several hundred transfers to result in one pregnancy （怀孕）．It takes a long time and it's difficult，but this could be（47）
science if it works．They are certainly not putting any live pandas at risk，so it is（48）
the effort，"adds Kraemer，who is one of the leaders of the project at Texas A&M，the first-ever （49）
at cloning a dog．
"They are trying to do something that's never been done，and this is very similar to our work in Noah's Ark．We're both trying to save animals that face extinction．I certainly （50）
their effort and there's a lot we can learn from what they are attempting to do．It's a research that is very much needed．"