Imagine putting a seed in a freezer, waiting 30,000 years, and then taking the seed out and planting it. Do you think a flower would grow? Amazingly, scientists have just managed to do something very similar. They found the fruit of an ancient plant that had been frozen underground in Siberia for about 31,800 years. Using pieces of the fruit, scientists successfully cloned 36 more of the plant and grew them in a lab. The new flowers have beautiful white petals . They are also the oldest flowering plants that researchers have ever revived from a deep freeze. "This is like creating a dinosaur from tissues of an ancient egg," University of California biologist Jane Shen-Miller said. The plant has a long history, back when mammoths ( an animal like an elephant, that lived a long time ago but no longer exist) wandered the land. It was buried in an underground hole. The ground has remained frozen since then. The ice-age plants look similar to a modern   called Silence stenophylla. But the ancient flowers are slightly different: their petals are a bit narrower. It's possible that the regrown plants belong to a different species. It's important for scientists to know that plant tissues can still be revived after being frozen for a long time. That's because many researchers are trying to store the seeds of modern plants by freezing them and then storing them in very big lockers at various spots around the globe. The Svalbard Global Seed Vault, an underground facility in Norway, stores hundreds of thousands of seeds. If a plant becomes extinct, scientists could revive it by pulling its seeds from Svalbard or other underground rooms. Many researchers are storing the seeds of modern plants   _  .
by spreading them around the world so that they can research them by burying them under the ground in case they die out some day
Question: Imagine putting a seed in a freezer, waiting 30,000 years, and then taking the seed out and planting it. Do you think a flower would grow? Amazingly, scientists have just managed to do something very similar. They found the fruit of an ancient plant that had been frozen underground in Siberia for about 31,800 years. Using pieces of the fruit, scientists successfully cloned 36 more of the plant and grew them in a lab. The new flowers have beautiful white petals . They are also the oldest flowering plants that researchers have ever revived from a deep freeze. "This is like creating a dinosaur from tissues of an ancient egg," University of California biologist Jane Shen-Miller said. The plant has a long history, back when mammoths ( an animal like an elephant, that lived a long time ago but no longer exist) wandered the land. It was buried in an underground hole. The ground has remained frozen since then. The ice-age plants look similar to a modern   called Silence stenophylla. But the ancient flowers are slightly different: their petals are a bit narrower. It's possible that the regrown plants belong to a different species. It's important for scientists to know that plant tissues can still be revived after being frozen for a long time. That's because many researchers are trying to store the seeds of modern plants by freezing them and then storing them in very big lockers at various spots around the globe. The Svalbard Global Seed Vault, an underground facility in Norway, stores hundreds of thousands of seeds. If a plant becomes extinct, scientists could revive it by pulling its seeds from Svalbard or other underground rooms. Many researchers are storing the seeds of modern plants   _  .
A. by spreading them around the world
B. so that they can research them
C. by burying them under the ground
D. in case they die out some day
Answer: