With only about 1000 pandas left in the wo

问题：

With only about 1000 pandas 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 been undertaking for the past five years in a project called "Noah’s Ark".
Noah’s Ark is aimed at collecting eggs, embryos, semen and DNA of endangered animals and storing them in liquid nitrogen. If certain species should become extinct, 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 reintroduce the species in the future.
It is estimated that as many as 2000 species of mammals, birds reptiles will become extinct in over 100 years. The panda, native only to China, is in danger of becoming extinct in the next 25 years.
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 implant the embryo into a host animal.
The entire procedure 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 (capable of being used) panda eggs could be a major problem, " Kraemer believes. "They will probably have to do several hundred transfers to result in one pregnancy (having a baby). It takes a long time and it’s difficult, but this could be groundbreaking science if it works. They are certainly not putting any live pandas at risk, so it is worth the effort, " adds Kraemer, who is one of the leaders of the Project at Texas A & M, the first-ever attempt 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 appreciate 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. \

According to Professor Kraemer, the major problem in cloning pandas would be the lack of ______.

A. available panda eggs
B. host animals
C. qualified researchers
D. enough money