Nola is a 41-year-old northern white rhino  that lives at the San Diego Zoo Safari Park in Escondido, California. She is one of only four remaining northern white rhinos in the world, and the only one in the western part of the earth. The other three live in Kenya . Rhinos have lived on earth for more than 40 million years, but they are now at the risk of dying out. Hunters illegally hunt rhinos for their horns , which are used for art, jewelry, and decorations. They sell the horns for thousands of dollars per pound, though it is not allowed by law. Rhino horns are also prized as a key part in traditional medicine, even though scientific tests have proven that the horns cannot cure illnesses. Experts say that every eight hours, one rhino will be hunted. Scientists are trying to find ways to prevent rhinos from dying out. In 1975, the San Diego Zoo Institute for Conservation Research started the Frozen Zoo, a program through which researchers have collected cell samples  from more than 8,000 different animal species until now, including the northern white rhino. Scientists hope that by studying the rhino cells, they will gain greater understanding of the species, and will find ways to increase its number. Jeanne Loring works with the Frozen Zoo. Loring's research focuses on pluripotent stem cells, which are cells that can renew and become any cell type. Loring's lab at TSRI is working together with scientist Oliver Ryder of the San Diego Zoo to use pluripotent stem cells to try to increase the number of the northern white rhino. Loring said the goal is to start producing new rhinos through this method over the next couple of years. We learn that pluripotent stem cells   _  .
can be easily stored don't exist in all animals can reproduce in a new form are dangerous to normal cells
Question: Nola is a 41-year-old northern white rhino  that lives at the San Diego Zoo Safari Park in Escondido, California. She is one of only four remaining northern white rhinos in the world, and the only one in the western part of the earth. The other three live in Kenya . Rhinos have lived on earth for more than 40 million years, but they are now at the risk of dying out. Hunters illegally hunt rhinos for their horns , which are used for art, jewelry, and decorations. They sell the horns for thousands of dollars per pound, though it is not allowed by law. Rhino horns are also prized as a key part in traditional medicine, even though scientific tests have proven that the horns cannot cure illnesses. Experts say that every eight hours, one rhino will be hunted. Scientists are trying to find ways to prevent rhinos from dying out. In 1975, the San Diego Zoo Institute for Conservation Research started the Frozen Zoo, a program through which researchers have collected cell samples  from more than 8,000 different animal species until now, including the northern white rhino. Scientists hope that by studying the rhino cells, they will gain greater understanding of the species, and will find ways to increase its number. Jeanne Loring works with the Frozen Zoo. Loring's research focuses on pluripotent stem cells, which are cells that can renew and become any cell type. Loring's lab at TSRI is working together with scientist Oliver Ryder of the San Diego Zoo to use pluripotent stem cells to try to increase the number of the northern white rhino. Loring said the goal is to start producing new rhinos through this method over the next couple of years. We learn that pluripotent stem cells   _  .
A. can be easily stored
B. don't exist in all animals
C. can reproduce in a new form
D. are dangerous to normal cells
Answer: